And Number 519-69-01-A (June 1, 1931 to June 30, 1932)

JOB DESCRIPTION

FINAL REPORT

State: New Mexico Project Number: E-1-3

Project Title: Endangered Species

Study Title: Status Investigation of Mollusks

Job No. 1 Program Narrative Objective No. 1 Contract Period: From: January 15, 1981 To: June 30, 1983 ( Amended)

ABSTRACT

A survey of the status of the living freshwater mollusks of New Mexico was done, using data from the literature, specimens, and field investigations. Fifty-one species of these mollusks in 10 families and two classes were recorded from the state, with all but three species being native. Of the native species,20 are so rare, local, or otherwise vulnerable that they could be considered as candidates for listing as state-endangered. Of these 20 species, six are so rare, local or otherwise vulnerable as to be possible candidates for federal listing as endangered or threatened--and five are endemic to New Mexico.

REPORT CONTENT

1. Objective:

a. To determine and report the status Of freshwater mollusks that may be endangered or threatened in New Mexico and to make recommendations on their conservation.

I I. Background:

The freshwater molluscan fauna of New Mexico has been subject to scientific i nquiry since the 19th century. However, no largescale, sy-stematic effort has been expended toward summarizing the status of this fauna, particularly from the point of view of species that may be endangered or threatened in the state. In view of the fact that mollusks are among the taxa which the New Mexico Department of Game and Fish is directed to conserve under the Wildlife Conservation Act (Chapter 17-2-33 through 17-2-46, Nt1SA 1973), a need has existed to gather data on the status of such animals in the state. Because of this need--as well as because of increasing threats to aquatic habitats in New Mexico an8 the potential loss of mollusks as a result--the present project was undertaken.

III. Procedures:

The bulk of this project was accomplished under a professional service contract between the Department of Game and Fish and Dr. Delight W. Taylor of San Francisco State University, Tiburon, California. Two contracts were effected, Number 519 - 69-01 (January 15, 1931 to June 30, 1931) and number 519-69-01-A (June 1, 1931 to June 30, 1932). The final report from Dr. Taylor was due June 30, 1982, but this JD-2

date was verbally extended to early 1983 to allow for more complete analysis and • reporting. The combined contracts provided for the following:

1. Compilation of a list of freshwater mollusks living in New Mexi co, incl uding those species that are potential candidates for federal and/or state listing as endangered or threatened, as defined under the Endangered Species Act (1973 and amendments) and/or the Wildlife Conservation Act (1974).

2. Preparation for publication of descriptions necessary for naming of any undescribed species that may be candidates for listing.

3. Provision of information relevant to the conservation of potential ly listable species.

4. Final report by candidate species, giving

a. scientific and common names. b. range overall and in New Mexico. c. relative abundance (New Mexico). d. habitat requirements (New Mexico). e. threats to survival (New Mexico). f. management recommendations (New Mexico). g. general description and taxonomic relationships. h. appropriate illustrations. I. other relevant information.

These items (1-4, above) were to be determined from appropriate fieldwork in New Mexico, specimen study, literature review, and related sources. Duplicate specimens of each treated species were to be provided to the Department of Game and Fish, along with copies of field sheets and other relevant written work notes. Fieldwork conducted by Dr. Taylor in New Mexico and under this contract was done in April-May and September- October 1 931. The following are among the localities visited for purposes of these contracts: a. Chaves County: Bitter Lake National Wildlife Refuge:. Pecos River; Roswell Country Club. b. Cibola County: Rio San Jose; San Rafael; Zuni Mountains. c. Colfax County: Black Lake ; Cimarron River. d. Eddy County: Black River; Blue Spring; Castle Spring; Geyscr Spring; Guadalupe Mountains; Pecos River. e. Grant County: Gila River. f. McKinley County: Nutria Creek and elsewhere in the Zuni Mountains. g. Rio Arriba County: Rio Grande; San Juan Mountains. Ii. Sandoval County: Jemez Mountains i. San Juan County: San Juan River j. San Miguel County: Conchas River, including reservoirs. k. Santa Fe County: Nambe Lake; Santa Fe Lake. 1. Socorro County: Alamosa River; Socorro Spring; Torreon Spring; Willow Spring. m. Taos County: Rio Grande n. Union County: Clayton Lake; Dry Cimarron River; North Canadian Creek.

I n addition, specimen collections from the following institutions were consulted by Dr. Tay lor: JD-3

a. Academy of Natural Science, Philadelphia, Pennsylvania. b. California Academy of Science, San Francisco. c. University of Colorado, Boulder. d. University of Michigan Museum of Zoology, Ann Arbor. e. University of Texas, El Paso. f. United States National Museum of Natural History, Washington.

Personnel from the New Mexico Department of Game and Fish participated in mollusk- col lecting and related to activities to a limited extent. The results of their efforts were incorporated into Dr. Taylor's findings.

I V. Findings:

Some 51 species of living freshwater mollusks were documented as occurring in New Mexico, with 4G of these being native and three introduced (latter marked by I, below). Of these 51 species, four appear to have been extirpated in New Mexico (marked by X) and one other may be extinct (marked by Z). Finally, 29 of the 48 native species are regarded as sufficiently rare, local, or otherwise vulnerable to be potentially endangered or threatened (E). In these 29 species, three distributional categories are recognized: endemic to Hew Mexico (NM), narrowly distributed, but not endemic (ND), and widespread but peripheral in New Mexico (P).

A. Class GASTROPODA

1. Assiminea species (a)--E(ND)

II. Fami ly Hydrobi i dae 2. Fontelicella neomexicana (Pilsbry)--E(NM) 3. Fontelicella species (a)--E(NM) 4. Fontelicella species (b)--E(NM) 5. Fontelicella species (c)--E(NM) 6. Fontelicella species (d)--E(NM) 7. Fontelicella species (e)--E(NM)

III. Family Littoridinidae U. Tryonia species (a)--E(NM) 9. Tryonia species (b)--E(NM)

I V. Family Lymnaeidae 10. Lymnaea caperata Say--E(P) 11. Lymnaea palustris group 12. Bakerilymnaea cubensis (Pfeiffer) 13. Bakerilymnaea techella (Haldeman) 14. Fossaria modideTITTS-30 — 15. Fossaria F.3773 (L-ea) 16. Radix auricularia (Linnaeus)--I

V. Family P1 anorb i dae 17. Gyraulus circumstriatus (Tyron)--E(P) 13. Gyraulus, crista (Linnaeus)--E(P) JD-4

19. Gyraulus parvus (Say) 20. Planorbella duryi (Weatherby)--I 21. Planorbella subcrenata (Carpenter)--E(P) 22. Planorbella tenuis (Dunker) 23. Promenetus exacuous (Say)--X 24. Promenetus umbilicatellus (Cockerell)--E(P) 25. Genus and species(a)--E(NM)

VI Family Ancylidae 26. Ferrissia californica (Rowell) 27. Ferrissca rivularis (Say)--E(P)

VII. Family Physidae 23. Physa gyrina (Say) 29. Physa virgata (Gould) 30. Physa species (a)--2(?); E(NM)

B. Class PELECYPODA

VIII. Family Unionidae 31. Anodonta imbecillis (Say)--E(P) 32. Cyrtonaias berlandieri (Lea)--X 33. Popenaias popei (Lea)--E(ND) 34. Uniomerus tetralasmus (Say)--X

I V. Family Corbiculidae 35. Corbicula fluminea

X. Family Sphaeriidae 36. Sphaerium striatinum (Lamarck)--E(P 37. Musculium TEcTriN3WIT-( Cooper)--E(P) 30. Musculium partumeium (Say)--E(P) 39. Musculium transversum (Say)--E(P) 40. Musculium truncatum (Gould)--E(P) 41. Pisidium casertanum (Poll) 42. Pisidium opmpressum Prime 43. Pisidium contortum Prime 44. Pisidium insigne Gabb 45. Pisidium lilljeborgi Clessin--E(P) 46. Pisidium pauperculum Sterki--X 47. Pisidium milium Held--E(P) 46. Pisidium singleyi Sterki--E(P) 49. Pisidium variabile Prime 50. Pisidium ventricosum Prime 51. Pisidium species (a)--E(NM)

Of the 51 species of freshwater mollusks recorded from New Mexico, ten appear to be undescribed species and one other is an apparent new genus. JD-5

The allocation of these new taxa is as follows:

a. Family Assimineidae: one new species in the genus Ass iminea. b. Family Hy drob i idae: five new species in the genus Fonteli ce 1 I a. c. Family Li ttori di nidae: two new species in the genus Tryon i a. d. Family Planorbidae: one new genus and species. e. Family Physidae: one new species in the genus Physa. f. Family Sphaeriidae: one new species in the genus Pisidium.

Dr. Taylor is in the process of describing these new taxa, and reprints of the descriptions and/or references to them will be avai lab le when they are published. In regard to the 29 species of mollusks recommended by Dr. Taylor as potentially endangered or threatened, 16 of these are relatively wide- ranging forms that are peripheral in New Mexico and 13 others are more narrowly distributed. Among the peripheral species, all but one are northern and/or eastern species that reach southern and/or western limits in New Mexico, i.e. Lymnaea caperata, Gyraulus spp. (2 species), Planorbel la subcrenata, Promenetus umbi 1 i catellus , Fe r ri ss i a ri vulari s , Anodonta i mbecillis, Sphaerium striatinum, Musculium spp. (4 species), and Pisidium spp. (3 species). One other species, Pisidium singleyi, is a southern species at i ts northern limits in New Mexico. Interestingly, of the four extirpated species, three are northern and/or eastern species that were at southern and/or western limits in the state: Promenetus exacuous, Uniomerus tetralasms, and Pisidium pauperculum. Cyrtonaias berlandieri is largely a Texas species, ranging narrowly into adjacent Mexico and at least formerly New Mexico. Of the 13 more narrowly distributed species, eleven are endemic to New Mexico, i.e. Fontelicel la spp. (6 species), Tryonia spp. (2 species), Physa sp. (1--undescri bed) , Pisidium sp. ( 1--undes cri bed) , and an undescri bed member of the family Planorbidae (new genus and species). Two other species occur in New Mexico and Texas (Assiminea, species undescribed) or these states plus Mexico (Popenaias p-oil7e7) —1.4171 le one of the endemic species--the Physa sp--maybe extinct. (Also see Cyrtonaias berlandieri , above). Details on the description, distribution, biology, status,and conservation of the above species are included in Appendix I (attached). These accounts were prepared by Dr. Taylor under the contracts outlined earlier. Incl)ided here are the 29 species recommended by him for possible consideration as endangered, plus four extirpated species that, had they persisted in New 'Mexico. would also be likely candidates for listing as endangered.

V. Analysis

The data assembled under this project have met the objective, and 29 species were recommended by Dr. Taylor to be considered as endangered under the Wildlife Conservation Act. After due consideration by the Department of Game and Fish, on February 15 and June 6, 1983, six of these species were recommended for listing under the Wildlife Conservation Act as Endangered (Group I) and 14 as Endangered (Group II). These species are as follows: JD-6

Group I 1. Assiminea sp. (undescribed) 2. Fontelicella neomexicana 3. Fontelicella sp. (d--undescribed) 4. Anodonta imbecillis 5. Popenaias popei 6. Musculium transversum

Group II 7. Fontelicella sp. (a--undescribed) 3. Fontelicella sp. (b--undescribed) 9. Fontelicella sp. (c--undescribed) 10. Fontelicella sp. (e--undescribed) 11. Lymnaea caperata 12. Tryonia -sp. (a=undescribed) 13. Tryonia sp. (b--undescribed) 14. Gyraulus crista 15. Planorbidae sp. (genus and species undescribed) 16. Musculium raymondi 17. Pisidium lilljeborgii 18. Pisidium partumeium 19. Pisidium ventricosum 20.. Pisidium sp. (a--undescribed)

Of these 20 species, six would appear to be suitable candidates for federal listing-- based on their rarity, localness, and/or other vulnerabilities. These species are as follows:

1. Assiminaea sp.--(possibly endangered). 2. Fontelicella neomexicana--possibly endangered. 3. Fontelicella sp. (a--undescribed)--possibly threatened. 4. Fontelicella sp. (d--undescribed)--possibly threatened. 5. Tryonia sp. (a--undescribed)--possibly threatened. 6. Planorbidae sp. (genus and species undescribed).

VI. Recommendations: The findings embodied in Dr. Taylor's report represent an excellent baseline for our understanding of the distribution, status, needs, and other aspects of the freshwater mollusk fauna of Hew Mexico. However, more survey work needs to be done, and the undescribed taxa need to be published as soon as possible. In the meanwhile, listing actions need to be pursued for the species outlined above, both at the state and federal level. Such listing will be an essential step toward the conservation of New Mexico's native freshwater mollusks, three-quarters of which are endangered, extirpated, or extinct.

....N ' / / l 1 1 4 1 .■ /".■ • j j Prepared b : •-•) if--4t I ' ii-otikA Approved by: Jo1-6 P. Hubbard Robert H. Stewart Pr6ject Leader FA Coordinator

ADD roved by: La, JD-7

APPEND I X J D- 8

FRESHWATER MOLLUSKS D. W. Taylor

The mollusks inhabiting fresh waters represent only two classes, the Gastropoda (snails) and Bivalvia (or Pelecypoda; clams) out of the larger number found in the sea. More than two patterns of reproduction, feeding, respiration and physiology are represented, so that the range of habitat, geographic distribution, life history, and threats to survival of the species are correspondingly varied. The endangered species in New Mexico belong to several such different biological groups. ' New Mexico has a known fauna of 48 native species of freshwater mollusks, a small number for the area of the state but understandable considering its arid and semi-arid climate. The distinctive aspect of the fauna is due largely to the number of localized endemic species--those restricted to one or a few springs or streams. The contrast with the fauna of Colorado is clear: New Mexico Colorado

Total number of species 48 45 Endemic species 11 0 Per cent endemic 23 0 These localized species imply a long history of isolation and evolution, and continuity of habitat in localized waters. The fossil record in the United States indicates virtually no evolution of freshwater mollusks in the Pleistocene (the last 1:2 million years). Many species now living can be recognized as Miocene fossils, more than 5 million years old. Hence most of the species in New Mexico, including the localized forms, began to differentiate from one to five or million years ago. The ancient origin of these species is a principal reason for their conservation. They are part of our heritage from the remote past. Another reason for conservation is that some of the species--all of them localized and threatened or extinct--are relics from a past landscape and climate far different from the present. Some are survivors from Pleistocene times when climate was cooler and wetter in New Mexico. Others represent a still older fauna distributed when drainage systems and landscape were unlike those of today. JD-9 Out of the 48 native species, 30.are considered endangered, potentially endangered, or of special concern. This is a higher percent than in any other of the western United States. The reason is the number of local endemic species, and other forms that occur outside New Mexico but are marginal within the state. Diversity of topography and drainage enrich the fauna with species found generally to the north and south:

More southern 4 More northern 14 Freshwater as well as terrestrial mollusks belong to several lineages that independently left the sea. One species in such a transition is Assiminea a. The genus is found over most of the world, principally in the upper intertidal zone and in coastal brackish waters. A few species are known in fresh waters. This Assiminea is semi-aquatic, semi-terrestrial, and lives in the continually moist border among sedges and grasses along the margins of springs. It is more remote from the sea than any other species of the genus. Its evolution from a presumed seaspore ancestor is thought to have taken place along a brackish ancegtral Pecos River. The gill is vestigial and the mantle-cavity may be air-filled, functioning as a lung.

Fontelicella and Tryonia are gill-bearing snails like Assiminea, but in them the gill is fully developed and they are strictly aquatic. Respiratory needs are presumably one reason both genera are characteristic of perennially flowing, well-oxygenated water. At present both are nearly restricted to springs and spring-brooks, but their extensive distribution in the western United States and northerr Mexico implies continuity of habitat in streams. For both genera the Great Plains have been impassable: the Pecos River is the easterr limit of range. Their near-restriction to perennial springs has been a major factor in speciation. Both genera are species-rich, with numerous localized species. But although the ranges of the genera overlap broadly, and their habitat can be described as perennial springs, they are hardly ever found living together and inhabit different types of springs.

Fontelicella is characteristically a rheocrene spring snail. It is most commonly found in a spring or spring-fed brookvith watercress, not even mildly thermal, with low content of dissolved solids. Thus it can live in the small streams of many mountain ranges in the west. Tryonia is often found in limnocrene springs. It is characteristic of mildly thermal springs, these generally having little or no watercress and a white crust of alkaline efflorescence along the water edge. The source waters rise from depth, hence such springs are in valleys rather than the mountains, and often near bounding faults. Fontelicella is usually in springs too small to support a population of fishes, but Tryonia is mostly in larger springs. Many of the species of Tryonia (nearly all narrowly localized) are associated with species of the pupfish, J D- 10 Cyprinodon, also localized.

New Mexico has more than its share of exceptions to the fore- going generalizations. Tryonia a lives ina group of rheocrene springs where the snails are found on stones rather than (as usual) in soft substratum. Fontelicella a and F. neomexicana are from slightly thermal waters. One of the few associations of the two genera is near Roswell, where Fontelicella d and Tryonia b inhabit the same non-thermal springs. Fontelicella e is the only species of the genus restricted to hot springs; it is found in the Gila River canyon near the Gila Cliff Dwellings, where it may be found on steep or even vertical rock faces in the spring outflow--also unique for the genus. In all these cases, changes of climate or landscape restricting the volume of habitable situations have probably shifted the species into atypical habitat.

The other species of New Mexican freshwater snails are all pulmonates, having a respiratory cavity that lacks gills and is called a lung. Some of the species may breathe air directly, but in those that live in a perennial-water habitat oxygen is probably taken from the water.

Aquatic mollusks that live in a seasonal habitat are practically all widespread species, whether they are snails or clams. The transient nature of the waters they inhabit requires them to resist desiccation by burrowing into the bottom and lying dormant. Desic- cation resistance is correlated with the ability for passive transport, by insects or birds. Individual ponds or marshes are geologi- cally ephemeral, and a species adapted for such habitats is adapted also as an opportunistic colonizer. Thus the seasonal-water species in New Mexico are mostly found at many places in the state. Only a few, at the margins of their ranges, are so limited in distribution as to be potentially threatened. The broad upland valley on the eastern side of the Sangre de Cristo range, from the headwaters of Cienega Creek south to Black Lake, is a specially favorable area and is the only part of the state where some species have been found.

Most of the seasonal-water species occurring marginally in New Mexico are of generally northern distribution: Lymnaea caperata, Gyraulus circumstriatus, G. crista, Promenetus umbilicatellus, Musculium raymondi. The New Mexico ramshorn snail, living in seasonal rock-pools, is exceptional in being localized. The widespread, northern snail Lymnaea caperata occurs in New Mexico in two widely distant localities and distinct habitats. The northern occurrence is in shallow, seasonal ponds in Valle Grande of the Jemez Mountains, a habitat common for the species in Colorado. The secord occurrence is far south, in Bitter Lake National Wildlife Refuge in the Pecos Valley. This is the southernmost occurrence of the species, evidently possible through the presence of a densely vegetated perennial seepage that provides shade and a summer-cool habitat. From its fossil record nearby, this population of Lymnaea JD-11

caperata is seemingly a Pleistocene relic.

In most of its extensive range in North America, Promenetus exacuous is found in habitats from perennial lakes or rivers to marshes subject to seasonal fluctuation. The one population in New Mexico (now extinct) was from San Rafael, in a habitat almost unique for the species, an artesian spring. This snail was far more widespread in the geological past, and as the climate became warmer and drier it died out except for the one colony insulated by the spring from summer heat. The habitat at San Rafael included not only this relic from the Pleistocene fauna of New Mexico but three others: the tiny clam Pisidium pauperculum, a meadow mouse, Microtus, and Physa a.

Some species of Physa live in shallow or even seasonal water and breathe air directly with a lung. The narrow range of Physa a suggests a different kind of respiration. Only two populations of the species have been known in modern times, both in New Mexico. The apparent restriction of the species to large springs leads to the supposition that it may have remained below the water surface at all times, respiring dissolved oxygen. Most species of Physa are widespread, hence the narrowly localized range of this species indicates some exceptional isolating mechanism.

All clams are confined to water while they are active by their life specialty of siphoning water for oxygen, and often filtering out food particles. The two groups native to New Mexico are different in life history, life span, feeding and reproduction.

Freshwater mussles (family Unionidae) attain a length of several inches, far more than other mollusks in the state. Their - size is correlated with a life span of several years. Adult mussels are found usually in perennial streams where they hardly ever move, filtering water for both food and oxygen. Yet as species they may be widespread. A larval stage, the glochidium, is ejected from the parent and can survive only if it attaches to a suitable fish host, sometimes a.single species. The fish hosts for Cyrtonaias berlandieri and Popenaias popei remain unknown. Both species are restricted in New Mexico to a segment of the Pecos River below Carlsbad about 10 miles long. Their modern occurrence in the state is indicated by fresh shells from the river banks, but no living individuals have been collected in recent years and they may have been exterminated by agricultural development and pollution.

Tiny clams of the genus Pisidium can be found in most parts of the world in fresh waters. They respire oxygen from a current of water drawn into the body, and select fine particles of food from the surrounding substratum. Most are probably annual, all have the sexes united in a given individual, and all bear live young. Range of habitat and geographic distribution vary widely by species. JD-12

STATE OF NEW MEXICO

II••••/0 an& • "IMO •••••• * • •

1 • • 1 • 15 • 19 ••• ••• •

0 • 6 •••••■ I i al N , 10 14 • • e 6 2 411JV • ,•••••••• r" NO••••

• WIIIIIMWO V • • C u C 1 • 6 0•1.18•C ...1

-- • •• • • 6 [ 4 3 5 • •

S 0 C * 4 0

j I C 0 I. 111 ' C 9 6

•••••••■ • • ! - • • •• • T /. C • • .11•119 • P ••• 9 8 2 14 " L 1

• 1 OMNI •

• 4= •

1 • • 2

NURBERS OF NATIVE SPECIES OF FRESHWATER MOLLUSKS IN NI MEXICO IN QUADRANGLES OF ANE DEGREE LATITUDE AND LONGITUDE NUNTERS OF 3 AND BELCW ARE AN INDICATION OF LACK OF COLLECTING. JD-13

Pisidium pauperculum is widespread in North America. - Primarily a river and lake species, it is a relatively large-water member of the genus. The one population known in New Mexico is extinct, a victim of groundwater development. Most species of Pisidium have considerable geographic ranges, and have long since been named. Thus the discovery of a new species high in the Sangre de Cristo range is altogether surprising. Pisidium a may be found in that part of the range that extends into Colorado, but collecting still further north has been so thorough that a more extensive range is unlikely. The accompanying map shows the number of native species found in the state according to quadrangles of one degree latitude and longitude. Although the fauma is richer in some areas than in others, lack of collecting is shown by those quadrangles with few or no species known. Thus futher additions to the fauna are practically certain. Some of these will be widespread species found in adjacent states, others new to science.

The known fauna of New Mexico, both native and introduced specie! is listed below in order of taxonomic classification. Summaries of the species that are endangered, threatened, or of special concern are grouped accordingly to their degree of threat. 1 JD-1 4

Pecos Assiminea (Assiminea a )

Distinguishing features: The shell is conical, pale pink in color, to 2.2 mm long, with broadly ovate aperture and wide umbilicus in the base. In life the snails are distinctive because the eyes are within short ocular peduncles, not long tentacles.

Scale 1 nun Other descriptive details: The sole of the foot is divided trans- versely into a shorter anterior and longer posterior portion. On the right side of the body is a conspicuous shallow groove running diagonally forward to below the base of the broad rostrum.

Distribution: Only one population is known in New Mexico, on Bitter Lake National Wildlife Refuge in Chaves County, where restricted to an area of less than 200 square feet. Another population was at Roswell Country Club, Roswell, where now extinct. ,The only other population known is at Diamond Y Spring, Pecos County, Texas, about 140 miles down the Pecos River valley.

Biology: No studies of biology or ecology have been made. The snails live on moist mud or vegetation within a few inches of running water, characteristically in the humid atmosphere beneath a mat of dead sedge blades. They do not live submerged in water, but either in a marginal film or just out of water. Respiration is probably by breathing air directly, as the gill is vestigial and the mantle cavity commonly has an air bubble inside.

Status: The one remaining population in New Mexico probably does not exceed 5000 individuals, and is extremely vulnerable because it is limited to such a tiny area. JD-15

Conservation: Protection of the population is maintained by present administration of Bitter Lake National Wildlife Refuge. The principal threat is burning of the vegatation below which the snails live.

Remarks: Assiminea is widespread in the tropical and warm-temperate regions of the world, almost exclusively along the edge of the sea or estuaries. The Pecos Assiminea lives further from the sea than any other species of the genus. J0-16

Socorro spring snail (Fontelicella neomexicana)

Distinguishing features: The penis bears glandular patches as follows: a terminal long Strip on the terminal lobe (T); a long, broad dorsal patch practically covering the free portion of the penis (DP); and three smaller dorsal - patches -- one diagonal on the right distal surface of the accessory lobe (D1), one diagonal on the left medial surface (D2), and one diagonal on the right proximal surface (D3); a ventral diagonal long strip (VL), and commonly a short transverse strip on the right side of the accessory lobe (V1). DI, D2, and D3 are all equally developed, in contrast to the consistently weak D2 of Fontelicella a.

Scale 1 mm Other descriptive details: The shell is tiny, elongate-ovate, up to 2.3 mm long, with a short, convex spire. The operculum is pale yellow.-brown, with a reddish-brown to amber internal callus.

Distribution: Warm springs at Socorro (now extinct), and Torreon - Springs, both Socorro County.

Biology: No studies of the biology or ecology of the species have been carried out. Species of the genus are characteristic of springs and spring-brooks, where they live among aquatic plants, on stones or in the uppermost layer of an organic mud substratum. They browse on the organic film on firm substratum, or select fine particles. The females are oviparous, and presumably lay eggs in the spring and summer. Fontelicella is practically never found in even midly thermal springs. At Socorro it probably did not co-exist with the Socorro isopod, Thermosphaeroma thermophilum (Richardson) that lives in warm water at the source of Sedillo Spring.

Status: The species was recorded originally as living at "Socorro, in warm springs." The collector and date of the unique first sample J D- 1 7 are unknown, nor is it certain just which spring or springs supported the population. Causes of extinction are uncertain, but they apparently eliminated the species before the metropolitan water development of recent decades. Torreon Springs have been impounded, eliminating the critical flowing-water habitat of the principal sources. One free-running spring remains, with an improved source pool less than 1 meter in diameter and an outflow stream less than 3 m long that includes all the species, estimated at less than 5000 individuals.

Conservation: The present situation of the species is extremely precarious. Even minor improvement of one tiny spring might eliminate the species entirely. Ideally, the headsprings would be restored by dropping the level of the impoundment and reestablishing running water habitat at the source. Failing this, the present spring should be strictly protected and efforts made to develop additional habitat. A spring-brook might be simulated in a ditch protected from stock and with aquatic vegetation such as watercress permitted to grow. Survi- val-of the species in such a situation would depend also on perennial oxygenated water within a suitable temperature range, unknown in detail.

Remarks: For maps of the thermal springs at Socorro, with history and details of flow and chemistry, see Summers (1976). J D- 1 8

Chupadera spring snail (Fontelicella a)

Distinguishing features: The penis bears glandular patches as follows: a terminal long strip on the .terminal lobe (T); a long, broad dorsal patch practically covering the free portion of the penis (DP); and three smaller dorsal patches-- one diagonal on the right distal surface of the accessory lobe (DI), one diagonal on the left medial surface (D2), and one diagonal on the right proximal surface (D3); on the ventral surface a transverse lobule bears a long glandular strip (VL), with sometimes a tiny dot-like glandular patch anterior to VL. D1 and D3 are equally developed, but D2 consistently weaker, unlike that of F. neomexicana.

Scale 1 mm J D- 19

Other descriptive details: The shell is indistinguishable from that of Fonteliceiii-TigEMexicana: tiny, elongate-ovate, with a short, convex spire. Other differences are that the operculum is a conspicuous deep red-brown color, unlike the pale operculum of F. neomexicana. Pigmentation of the body is intense: commonly the area of head and tentacles is black and the eyes cannot be distinguished. Distribution: Willow Spring, Socorro County.

Biology: See under Fontelicella neomexicana.

Status: The species is stable under present conditions, but as only one population is known it is potentially endangered. The snails. are abundant in the spring sources.

Conservation: The single population is on the privately owned Cienega Ranch and well protected ("No Trespassing. Survivors Will Be Prose- cuted."). The spring emerges on a hill slope and is safe from impoundment. Under present land use (stock grazing) no threats to the species are posed. Possible threats are either extensive distur- bance of the spring sources or drawdown of the water table by pumping, neither appearing likely in the immediate future. JD-20

Gila Spring snail (Pontelicella b)

Distinguishing features: The penis bears glandular patches as follows a terminal long strip representing the left and central portions of the usual terminal strip, and a papule (Tr) representing its right end; on the dorsal surface a long strip on the dorsal aspect of the free penis (DP); a second long strip (Dpi) extending from the left dorsal aspect of the free portion of the penis onto its left side; on a prominent dorsal distal lobule an arcuate or semicircular long strip (DDL); a long strip on the left distal margin of the accessory process (D1); on the ventral surface a long strip (VL) on the ventral lobule.

DPI Ti DDL

Scale 1 mm JD-21

Other descriptive details: The shell is elongate-conic, pale brown in color, reaching a length of 4mm with 4 3/4 whorls.

Distribution: Two springs in the Gila River drainage, Grant County, both just inside the Gila Wilderness. The principal locality is a group of cool springs in the center of sec. 3, T. 13 S., R. 13 W., unsurveyed, in immediate proximity to hot springs. The second locality is a thermal spring on the east side of the Gila River, in the NE4 SA sec. 17, T. 13 S., R. 13 W., unsurveyed.

Biology: No studies of biology or ecology have been made. The habitat at the principal locality is that typical for the genus: cool springs and spring-brooks. At the thermal spring locality the species is rare. At both places it is associated directly or nearly so with the New Mexico hot spring snail, but does not occur in as warm water, nor on rock surfaces. Status: At the cool-springs locality this species is abundant, the population consisting of several tens of thousands of individuals. At the warm-spring locality the number of individuals may be only a few hundred. JD-22 Pecos spring snail (Fontelicella c)

Distinguishing features: The penis bears glandular patches as follows: a terminal long strip on the terminal lobe (T); a long, narrow dorsal patch on the distal right surface, extending onto the posterior part of the free penis (DP); a dorsal distal lobule often bearing a tiny glandular patch (D1); on the ventral surface a small glandular patch (V1).

Scale 1 mm (left), .5 mm (right) Other descriptive details: The shell is narrowly elongate, up to 3 mm long with 5 1/4 whorls, and a relatively long, conical spire.

Distribution: Blue Spring and Castle Spring, Eddy County.

Biology: No studies of the biology or ecology of the species have been carried out. For general remarks see under the Socorro spring snail, Fontelicella neomexicana.

Status: A large population of hundreds of thousands of individuals lives at Blue Spring, where it is stable under present conditions. Only much increased development of ground water is a plausible threat, unlikely in the immediate future. At nearby, much smaller Castle Spring the population is correspondingly small. Drawdown of the water table is a greater threat, or even an un- usually severe flood.

Conservation: Preservation of Blue Spring in its present natural state will protect the species. Current land use (stock grazing) is consistent with preservation. JD-23

Roswell spring snail (Fontelicella d)

Distinguishing features: The penis bears glandular patches as follows: a terminal long strip on the terminal lobe (T); a Y-shaped penial gland (DP) with two posterior limbs, the anterior limb extending onto the left side of the free portion of the penis; a dorsal distal lobule (DDL) often bearing a small patch; and a ventral lobule (VL) with a strip that is usually transverse.

Other descriptive details: The shell is narrowly elongate, up to 3.8 mm long with 5 whorls and a spire with convex outline. Often there is a gland on the dorsal left medial surface of the penis, in addition to those illustrated. Distribution: Known only from Chaves County. One population is in a spring at Roswell Country Club, northeast of Roswell, three others in springs or seepages in Bitter Lake National Wildlife Refuge.

Biology: Seasonal life history and local distribution of this species were studied near Roswell by Noel (1954; as Amnicola neomexicana, the locality has not been relocated but the population is believed extinct The snails were abundant only in swift water of a springhead, on lime- stone rubble with a coating of organic detritus and algae. Below the source, in slower current, they were scarce. The annual population curve was irregular, but largest numbers were found in October to December.

Status: Populations on Bitter Lake National Wildlife Refuge are stable under present conditions, but far smaller than those of the often associated Tryonia b. The population at Roswell Country Club is marginal. Probably the species occurred commonly in springs of the Roswell area before. drawdown of the water table through agricultural development.

Conservation: The three populations on Bitter Lake National Wildlife Refuge are protected under present administration. The future of the small population at Roswell Country Club is insecure. Threats include alteration of the spring by landscaping, runoff of pesticides or dumping of toxic materials. The critical habitat of flowing water is limited to about 20 feet between spring sources and the slack water at the edge of an artificial lake. Ponding of the remaining free- running flow could eliminate the population.

Remarks: Shells of the Roswell spring snail and Koster's spring snail can look much alike, and the two species may be difficult to separate when bodies are withdrawn into the shell. The dark amber operculum of the Roswell spring snail contrasts conspicuously with the pale operculum of the other species. JD-25 New Mexico hot spring snail (Fontelicella e) Distinguishing features: The shell is small and broadly conical, attaining a length of 2.0 mm. The penis bears glandular patches as follows: a semicircular or horseshoe-shaped long strip, open dorsal- ly, on the terminal lobe (T); on the dorsal surface a long fishhook- shaped gland, composed of a wider penial (DP) portion continuous with a long, narrower curved strip (Dp) extending to the left distal margin and enclosing a few (commonly 3) strips generally oblique to the long axis of the penis; on the ventral surface no lobule, but a transverse strip (V) close behind the terminal lobe. DP

Scale 1 mm Other descriptive details: The planes of the shell aperture and growth lines are oETIFITIT: Eyes are in a clear halo, with no granular concentration forming an "eyebrow" as usual in the genus.

Distribution: Two hot springs of the Gila River drainage, Grant County, both just inside the Gila Wilderness. The type locality is on the east side of the Gila River in the NE 1/4 SW 1/4 Sec. 17, T.I3 S., R. 13 W., unsurveyed. The second locality is in the center of Sec. 3, T.13 S., R. 13 W., unsurveyed.

Biology: No studies of the biology or ecology of the species have been carried out. At the type locality the snails occur in a situation not known in other species of the genus: on steep and even vertical rock faces above the river, and in water as warm as 38° C, though probably mostly in a cooler film 33 -35° C. At the second spring the species occurred similarly to 38° C., but mostly in cooler waters where a thin sheet flowed down steep or even vertical faces. Cool springs issue in the same aroa as the thermal springs, but contained none of this species.

Status: At both the known localities the species is abundant, populations reaching several hundred thousand. Jo-26

Conservation: The species is within the Gila Wilderness Area, and protected under present administrative policies.

Remarks: The hot-spring habitat of the species is unique in the genus, as is its occurrence on steep or even vertical rock. The broadly conical shell with relatively large, oblique aperture can plausibly be interpreted as part of the adaptation to life on rock faces. The development of a larger foot, greater area of purchase • on the rock, and more compact shell are similar to the adaptations occurring in other groups of snails. The pattern of glands on the penis is quite unlike that known in other species of the genus, hence a long independent history of the species seems implied. J D- 2

Alamosa spring snail (Trvonia a)

Distinguishing features: The conical shell is up to 3 mm long, with well impressed sutures separating regularly convex whorls. The penis is a flattened blade with a conical papilla on the left side towards the tip.

Scale lmm for upper and lower left figures; .51mn for lower right JD-2C

Other descriptive details: A narrow umbilical chink is present adjacent to the ovate aperture. Live snails appear dark gray to black from color of the body, but empty shells appear pale tan (when fresh) or white. Sexual dimorphism is pronounced, with females attaining a size nearly twice that of the males.

Distribution: Known only from a group of thermal springs near the former Fort Harmony, at the head of.perennial flow in Alamosa Creek, in Socorro County.

Biology: Females are ovoviviparous, containing a series of embryos in various stages of development. Recruitment of the populations is assumed to be continuous, as there is little seasonality in the thermal spring habitat. The snails are most abundant on stones, gravel, and in vegetation, where they presumably browse on the organic film growing on the surface.

Status: The snails are abundant in two populations, one at Ojo Caliente, the other at an improved source about one-half mile to the west. They are restricted to the source area of the springs, in slow- moving current.

Conservation: The two populations of the species are stable under present conditions. Potential threats include development of the springs in such a way as to eliminate the surface flow of exygenated water and the organic film on vegetation and stones (by capping the spring; by impoundment; by drawing down the water table by pumping). Present land use in the area is for stock grazing, and this is compatible with maintenance of the species.

Remarks: Trvonia is widespread through the southwestern United States and-in—YEithern Mexico, characteristically in thermal springs. Nearly all species are found in soft organic mud, where they presumably select fine particles for food. The present species is distinctive in the genus because of its relatively broadly conical shell, single penial gland, and habitat on stones or other firm substratum. These features imply a long history cf isolation and evolution. JD-29

Koster's spring snail (Tryonia b)

Distinguishing features: The narrow elongate shell is up to 4.5mm long, with incised sutures separating regularly convex whorls. The penis is a flattened blade with a wide papilla on the left side towards the tip, wider and with a smaller gland than in Trvonia a. The penis is narrower at the base and tapers more gradually than that of Tryonia a.

Scale .5 mm (left), 1 mm (right)

Other descriptive details: An umbilical chink is present next to the ovate aperture. Live snails appear pale to nearly black from color of the body, but empty shells are pale tan (when fresh) or white. Sexual dimorphism is characteristic; males are about three- quarters the size of females.

Distribution: Known only from Chaves County. One population is in a spring at Roswell Country Club, northeast of Roswell, four others on streams and springs in Bitter Lake National Wildlife Refuge.

Biology: No studies of biology or ecology have been carried out. Females are ovoviviparous, containing a series of embryos in various stages of development. The springs and streams on Bitter Lake National Wildlife Refuge have soft substrata, and the snails are abundant in the upper layers where they presumably select fine particles. In the spring at Roswell Country Club the species can be found also on pebbles and among vegetation; perhaps here feeding is partly by browsing on the organic film on these surfaces as well as by selec- tion of particles. JC1-130 Status: Populations on Bitter Lake National Wildlife Refuge are large, and occur both above Bitter Lake (Lost River, Sago Spring) as well as below.The population at Roswell Country Club is marginal.

Conservation: The four populations on Bitter Lake National Wildlife Refuge are protected under present administration. The future of the small population at Roswell Country Club is insecure. Threats include alteration of the spring by landscaping, runoff of pesticides or dumping of toxic materials. The critical habitat of flowing water is limited to about 20 feet between spring sources and the slack water at the edge of an artificial lake. Ponding of the remaining free-running flow could eliminate the population.

Remarks: Tryonia b is not so broadly conical as Tryonia a, but nevertheless more so than most species of the genus. In shape it is much like the associated Fontelicella d, and the two species may be difficult to separate when bodies are withdrawn into the shell. The dark amber operculum of Fontelicella d contrasts conspicuously with the pale operculum of Tryonia in such cases. Say's pond snail (Lymnaea caperata)

Distinguishing features: The shell is elongate, up to 20 mm long, with whorls separated by well-impressed sutures. Spiral sculpture consists of erect bands of periostracum that are slightly undulating, irregular in detail, and spaced at roughly equal intervals. Each band is seated in an incised groove in the calcareous part of the shell beneath the periostracum. Along the crest of each band are slender, tapering setae spaced roughly equally. The projecting periostracum is worn readily, so that fine details are ordinarily visible only on the more recently formed shell surface, near the aperture.

Scale 6 mm

Other descriptive details: Spiral sculpture overrides the irregular weak axial threads, forming a reticulate pattern. There are no series of spirally aligned crescents as in many other species of the family.

Distribution: Widespread over much of northern North America; southward in the Rocky Mountains as far as New Mexico. Known in the state from two populations, one in the Jemez Mountains, Sandoval County, the other in the Pecos River valley in Chaves Courity.

Biology: No studies of life history or ecolbgy have been carried out. The species is generally found in ditches, marshes, and small streams that become dry seasonally. In the southern part of its range, in Colorado, it is found in such situations on the Plains and in lower valleys, and also in a different habitat: small ponds at high elevations. The New Mexican occurrence in the Valle Grande of the Jemez Mountains, Sandoval County is of this type. The snails were the only species of mollusk present in shallow seasonal ponds formed by earth slumping on the flanks of a hill at 8500 feet elevation. The ponds were only 50-75 feet in diameter. The other occurrence in New Mexico is unusual: a small perennial seepage at the edge of the Pecos River Valley on Bitter Lake National JD-32 Wildlife Refuge in Chaves County. This population is the southernmost known, and interpreted as a relic of Pleistocene times. The snails are restricted to an area of less than 200 square feet, where they survive in the summer-insulated environment beneath a dense growth of sedges in relatively cool water.

Status: Both populations in New Mexico are small, less than a few thousand individuals in both cases. The population in Bitter Lake National Wildlife Refuge is extremely vulnerable because it is limited to such a tiny area. Formerly the species was more widespread in the immediate vicinty, but its habitat has been largely eliminated by construction of drainage ditches along the western edge of the valley.

Conservation: The population in the Jemez Mountains is adequately protected under present land use (stock grazing). The population in Chaves County is protected by present administration of Bitter Lake National Wildlife Refuge. The principal threat is burning of the vegetation below which the snails live.

Remarks: Both populations in New Mexico are far distant from other occurrences of the species, and both are evidently relicts from Pleistocene times when the species was more widespread. • Tryon's ramshorn snail (Gyraulus circumstriatus)

Distinguishing features: The shell is up to 4 mm in diameter, with 4 whorls, Tdanispiral, with nearly plane sides. The whorls are nearly round in cross-section, enlarging slowly and regularly. There may be a callus thickening of the shell around the inner rim of the aperture.

Scale 1 mm

Other descriptive details: The aperture is only slightly wider than high. Sculpture consists of fine growth lines. Faint spiral incised striae may be visible in some specimens.

Distribution: Widespread in northern North America; southward at higher elevations to the mountains of southern California, central Arizona, and northern New Mexico. In New Mexico only two populations are known, in the southern Sangre de Cristo Mountains, Colfax County.

Biology: No studies of the biology or ecology of the species have been carried out. Published information is unreliable, as the species has been misidentified so often. It is characteristic of seasonal habitats, such as marshes, temporary ponds, or seasonal pools along the margins of lakes or streams. A latitude/altitude plot of localities of the species west of longitude 100 degrees and east of the Sierra Nevada-Cascade Range shows a generally straight lower edge. An early record from Albuquerque (not precisely localized) dating from the last century evidently represents an unusual situation (symbol labeled A). Possibly this is even from the same area as a similarly unusual JD-34

occurrence of Promenetus umbilicatellus. Locality B is from Pecks Lake, Arizona, where the species presumably lives in a habitat affected by spring-fed seepage.

Status: One of the two living populations is in the extensive marshes around Black Lake, where the area of suitable habitat is large. The other population is smaller but substantial.

Conservation: The population around Black Lake is stable under present conditions of land use (stock grazing). Homesite development has begun in the immediate area. Potential threats are degradation or modification of the habitat associated. with real estate development, such as drainage of the habitat or'application of pesticides. The second population is along Cimarron Creek, in an area under protection by the State Department of Game and Fish.

I T e 1r ri u d t i i's th :=gead G;r:Eril ; anti ": t;j . ZrM n ontoiat Le s : size, but differs by having more rapidly enlarging whorls and a less nearly symmetrical form. The right side is nearly plane, but the left side is broadly concave and the whorls are slightly flattened. Thus the aperture of G. Eanas is relatively wider and oblique compared to that in GT—circumstriatus. An apertural callus is unknown in G. parvus, and common but not consistent in G. circumstriatus. J D-35

Linnaeus' ramshorn snail (Gyraulus crista)

Distinguishing features: The shell is discoidal, tiny (about 2 mm in diameter), wiTEE-2-774 whorls, a plane or barely convex right side, and a deeply concave left side. The greatest diameter is not in the midline, but at the bluntly rounded margin closer to the right side. Commonly the growth ridges are expanded at intervals into narrow crests.

Scale 1 mm

Other descriptive details: The concavity on the left side is steep- sided. Fine spiral incised lines are visible at high magnifications.

Distribution: Circumboreal; widespread in northern North America, ranging southward as far as New Mexico. The one locality known in the state is in Colfax County, in the marshes around Black Lake.

131.2121z: Little is known of this snail, even though it was described by Linnaeus and is found in both Europe and North America not far from major universities. In Michigan Kenk (1949) found it was abundant for part of the spring in a temporary pond, but for most of the year remained buried in the mud bottom. The species seems to be characteristically a vernal form, locally abundant in seasonal ponds, but rare and sporadic in permanent water bodies. Status: Known from only a single population in New Mexico.

Conservation: The population is within private land used at present for stock raising, but homesite development has started in the immediate area. Current land use is compatible with preservation of the habitat and the population. Potential threats are degradation or modification of habitat associated with real estate development, such as drainage of the habitat or application of pesticides. J D- 36

Carpenter's ramshorn snail (Planorbella subcrenata)

Distinguishing features: The shell is planispiral, up to 30 mm in diameter, with sculpture of fine raised threads. The outer lip is broadly and regularly curved, and the whorls in cross- section are rounded.

Scale 5 mm

Other descriptive details: The left side of the shell is shallowly concave, with the early flat-sided whorls forming a roughly even surface. The right side has a narrow pit bordered by rounded surfaces.of the whorls.

Distribution: RockyMountain states, Pacific Northwest, and northern Great Basin; southward at higher elevations to northernmost New Mexico; isolated more southern occurrences in the San Bernardino Mountains, southern California, and in northern Arizona. Northern and eastern limits uncertain. In New Mexico in the southern Sangre de Cristo Mountains , Colfax County.

Biology: Taxonomic uncertainties cloud the interpretation of published information. Possibly there are no studies of the species. JD-37

In the more southern areas of occurrence (California, Nevada, Arizona, Colorado, New Mexico) the usual habitat is lakes and ponds, especially at higher elevations. Northward the range of suitable situations is broader, and the snails are found in marshes, rivers, and ditches. Status: Only two populations are known in the state, one in the marshes around Black Lake, the other on the lava plateau to the east.

Conservation: Both populations are on private land, where present use (stock grazing) is consistent with stability of the populations. In the Black Lake area homesite development has started, and potential threats there include drainage of the habitat or application of pesticides.

Remarks: The taxonomic status of this form is uncertain. The widespread species of New Mexico is Planorbella tenuis (Philippi), distinct from subcrenata by never reaching such a large size, by having a diagonally flattened outer lip, flatter whorls on the right side, and by occurring in a variety of habitats from ditches and streams to seasonal ponds and reservoirs. P. tenuis occurs also in trans-Pecos Texas (in the Davis Mountains), ãnd is the common species from Calif- ornia south over the Plateau of Mexico.

In south Texas the Planorbella present is P. trivolvis lenta (Say). It is distinguished by the reticulate sculpture of the early whorls on the right side, bordering and within the narrow spire pit, by the rounded whorls, and greater height relative to shell diameter. This form is found barely into trans-Pecos Texas (Independence Creek), and eastward across at least much of the Gulf Coastal Plain.

All these three forms appear distinct by shell features, and occupy different range of habitats, and have mutually exclusive distributions. Modern morphological studies are lacking since the incomplete (posthu- mous) work by Baker (1945). Although Baker ranked lenta as a subspecies of trivolvis, and subcrenata as a distinct species, Clarke (1973) viewed subcrenata a7-7013"i, -gubspecies of trivolvis. Postibly the species trivolvis of various writers is a composite. JD- 33

Keeled ramshorn snail (Promenetus exacuous)

Distinguishing features: The shell is up to 5 mm in diameter with 3 1/2 whorls; fiETTEUTTr, with a sharp median keel. The right side is gently convex or plane, the left side with a central depression with sloping sides.

Scale 1 mm

Other descriptive details: The margin of the aperture and the growth lines are strongly recurved toward the keel. Sculpture consists of fine growth lines, and irregular raised threads or narrow bands parallel to the growth lines.

Distribution: Widespread in northern North America; southward to western Nevada, Colorado and Nebraska. South of this range there were three isolated occurrences, associated with artesian springs • that provided local oases in Kansas and New Mexico. In New Mexico known only from Ojo del Gallo, San Rafael, Cibola County, where now extinct. Biology: Promenetus exacuous can live in a variety of water bodies, from perennial slow-moving ZFeeks and rivers to ponds and lakes, and in marshes and seasonal ponds or swales. It is found characteristically with a dense growth of submergent aquatic plants, and in "rich" habitats-- those supporting a relatively large number of mollusk species. Local distribution was studied in southern Manitoba by Pip and Pau1ishyn(1971). They found that the snails occurred irregularly; in water not much deeper than 1 m, and where the substratum was neither clay nor rock. Maximum temperature at which the species occurred was 26.5° C-- a limit consistent with the interpretation that summer maxima help determine the southern margin of distribution.

Status: Possibly surviving in the northern part of the state, as J D- 39

the nearest record is in the Rio Grande valley of southern Colorado. Even in Colorado this species is known from only a few scattered localities, hence few if any populations are expected in New Mexico. Judging by the number of shells om spoil piles around Ojo del Gallo, that spring supported a substantial population.

Conservation: The population at San Rafael is extinct, but the cause of extinction can be documented and preventive measures outlined. The former discharge of Ojo del Gallo was about 3100 gpm. Flow began to decrease in the mid-1940's due to ground-water development for agriculture in the Bluewater area. The spring became dry in 1953 (Gordon 1961).

Outflow of the spring supported an isolated population of the Colorado Meadow Mouse, Microtus pennsylvanicus modestus (Baird). "The southernmost locality at which they have been found isSan Rafael, where there are extensive marshes fed by big springs" (Bailey 1931). The spring- fed pond was the habitat of two other species of endangered mollusks; Pisidium pauperculum Sterki, known in New Mexico from only this one locality; and Physa a, known from only two populations anywhere.

Preservation of the habitat at Ojo del Gallo, biologically unique in New Mexico, could have been accomplished by substituting a pumped well for the artesian spring.

Remarks: Fossil occurrences of Promenetus exacuous are not uncommon in Pleistocene deposits of the Great Plains, south of its present range, and in central New Mexico, Evidently it was widespread at past times of cooler summers and greater rainfall, and has survived to the present in a few local spring-cooled habitats. At San Rafael the species was a Pleistocene relict.

Similar conclusions apply to the meadow mouse, Microtus. Anderson (1961) stated that "there is no doubt that most of the area between the known colonies in New Mexico is not suitable for Microtus pennsylvanicus and that the marginal colonies are relicts of a distribution that at some pluvial period of the Pleistocene was morA Widespread."

Next to San Rafael, the southernermost relict population of Promenetus exacuous is in artesian springs in Meade County, southwestern Kansas. Here too the springs supported extensive marshes, and in them was found an endemic bog-lemming, Synaptomys cooperi paludis Hibbard and Rinker (1942). JD-4O

Cockerell's ramshorn snail (Promenetus umbilicatellus)

Distinguishing features: The shell is up to 6 mm in diameter, with 4 whorls, planispiral, with rounded outer margins. The right side is plane or slightly concave, the left side with a central, steep-sided depression.

Scale 1 mm

Other descriptive details: The aperture is clearly wider than high, in contrast to some other ramshorn snails. Sculpture consists of fine growth lines, and spiral incised striae.

Distribution: Widespread in northern North America; 'southward at higher elevations to the mountains of central Arizona and northern New Mexico. In New Mexico only one population is known to survive, in the Canjilon Lakes area of Rio Arriba County.

Biology: No special studies of the biology or ecology of the species have been carried out. Mozley (1932, 1936) studied the fauna of temporary ponds on the southern plains of Canada, that contain water for only one or two months of the year. Promenetus umbilicatellus is characteristic of this habitat, and rarely associated with any except three other species of snails.

The most clear-cut habitat partitioning by the small Planorbidae Gyraulus and Promenetus has been observed in small ponds on the JD-41

Mogollon Rim in Coconino County, Arizona, at an elevation of about 7,500 feet. Here a zonation of species was evident. Promenetus umbilicatellus occurred closest to the rim, where water persists for the shortest length of time. Next towards the center, overlapping but largely separate, came Gyraulus circumstriatus. In the largest pond where water is practically permanent Gyraulus parvus occurred, again overlapping G. circumstriatus but largely separate.

A latitude/altitude plot of localities of the species west of longitude 100 degrees shows a generally straight lower edge. This plot supports the interpretation that summer maximum temperatures limit the margin of distribution in the western United States. The anomalous outlying occurrence was south of Albuquerque (A), and evidently represents an exceptional situation. Most likely it was a population temporarily established after floods of the Rio Grande.

Status: A second modern population formerly existed in the Jemez Mountans, Sandoval County. Alteration of habitat following construction of stock ponds probably eliminated the species in that case. Other populations are likely to be found in mountains of the northern part of the state.

Conservation: Like other vernal species, this snail is preadapted as an opportunistic colonizer of suitable habitats as they appear. No special conservation measures are warranted. JD-42

New Mexico ramshorn snail (planorbidae a)

Distincuishing features: The shell is planispiral, with 31/2 whorls, reaching a diameter of 4.5 mm, and nearly biconcave. The right side is broadly and regularly concave, but the left side has a steeper-sided central concavity a little over a third of the shell diameter. The aperture is roughly semi-ovate, asymmetrical, with the left side narrower than the right. The shell surface is glossy at first, with very fine growth lines, becoming silky or dull on later whorls with the growth lines becoming fine raised threads or even riblets.

• Scale 1 mm

Other descriptive details: Fresh shells are pale tan and translucent. In living animals dark blotches on the mantle are visible through the shell.

Distribution: Pecos River drainage, southeastern New Mexico.

Biology: Like the related species Promenetus umbilicatellus, this snail is characteristic of seasonal waters. It has been found living at only three localities, in each case in seasonal rock pools. Pre- sumably the snails survive buried in mud in the bottom of the rock basins, then emerge and begin a new generation when rains regenerate the pools.

Status: One population occurred formerly in a seasonal arroyo northwest of Santa Rosa, Guadalupe County, where it was collected by the late Junius Henderson in 1929. No suitable habitat is available now, and it seems probable former rock basins have been covered by Inter- state Highway 40. The two other known populations in the Guadalupe Mountains, Eddy County, are small, but it seems likely that others will be discovered in the vicinity. J D-

Conservation: The two known populations are stable under present conditions of land use (stock raising). Potential threat is greatest from possible construction of artificial ponds that could eliminate the seasonal-pool habitat.

Remarks: Species of seasonal-water habitat are usually widespread. Hence it seems likely there are special features that are responsible for the narrow range of this form. JD-44

Say's river limpet (Ferrissia rivularis)

Distinguishing features: The limpet-shaped shell is elliptical in outline, up to 6 mm long, with a blunt apex slightly to the rear and right of center. The posterior slope of the outline is gently concave, the anterior slope convex.

Scale 1 mm Other descriptive details: The apex of the shell, when clean, can be seen ornamented with very fine radial sculpture.

Distribution: Southern Canada and northern United States; southward in the Rocky Mountains to the Rio Grande. In New Mexico found only in the Rio Grande canyon above Velarde, Rio Arriba and Taos Counties.

Biolocv: The species has been studied extensively in New York state by Russell-Hunter and his students (Burky 1971, Russell- Hunter 1978, Russell-Hunter et al. 1967,1970). More is known about this species than most other American freshwater mollusks.

Genetically controlled inter-population differences occur in calcium uptake, shell protein content, enzyme polymorphism (9 loci), shell growth ratios, and perhaps rate of egg-production.

Unlike most pulmonate snails, with a one-year life cycle, Ferrissia rivularis may have either one or two per year. In the annual population, egg-laying began in April, lasted about 15 weeks, with capsules deposited containing an average of over one egg. In the semi-annual population studied by Burky, egg-laying began about the same time but lasted about seven weeks, with an average of over J D- 45

three eggs per capsule. The summer generation began spawning in early July for about seven weeks with a reduction in eggs per capsule to less than half that of the spring generation. Transfer experiments suggested partly environmental, partly genetic control of breeding.

Ferrissia lives in perennial fresh waters, in lakes or streams, on firm substratum such as pebbles, cobbles, cat-tail or sedge blades, or the lower surface of water-lily pads. In streams the snails are found characteristically on lower surfaces of cobbles and bould- ers, where sediment is minimal and organic film provides food. At one creek locality studied by Burky, in New York, Ferrissia appeared to be the dominant primary consumer.

Status: Only one population is known in New Mexico, but this is extensive, probably inhabiting the whole length of the Rio Grande from the state line to the mouth of the canyon in Rio Arriba County.

Conservation: The present protection of the river for fishing and recreational use is consistent with maintenance of the species. Poisoning of the river to eliminate unwanted fish species is the only foreseeable hazard.

Remarks: Ferrissia rivularis differs from F. californica (more widespread in New Mexico and the Southwest in general) by nearly regular elliptical outline, larger size, and more nearly central apex. In F. californica the right posterior part of the outline is distinctly flattened; the shell rarely exceeds 3 mm in length; and the apex is about one—fourth the shell length from the posterior end.

In the Rio Grande Canyon, Ferrissia rivularis is common locally and almost the only species of mollusk. This segment of the stream may be the only river in the United States characterized by this small river limpet. JD-46

Ashmun's Physa Snail (Physa a)

Distinguishino features: The shell is globose-ovate, to 18mm long, with an expanded body whorl, broadly rounded outer lip of the aperture, and very short spire.

Scale 2 mm

Other descriptive details: The inner lip at the anterior part of the aperture is nearly straight or with a weak fold. The surface texture of the shell is silky to glossy from the very fine axial threads and very fine spiral incised lines. Color of freshly collected shells is pale tan.

Distribution: Known only in New Mexico, from two populations. One was in Ojo del Gallo, San Rafael, Cibola County. The other at "Block Ranch, near Bland" has not been relocated.

Biology: No studies have been made. Localized species of Phvsa are rare, and most likely there is a physiological characteristic responsible for restriction of the species to large-spring habitats.

Status: The population at Ojo del Gallo is extinct, and the loca- tion and status of the other population unknown.

Conservation: See under Promenetus exacuous.

Remarks: Museum specimens collected alive by Rev. E. H. Ashmun in the last century at "Block Ranch, near Bland" are evidence of a second population. In those early days there were few reference points and the locality was almost inevitably vague. The mining town of Bland (now abandoned) was in Sandoval County, and that Block Ranch was presumably closer to Bland than to any other population center of the time. JD-1+7

Paper-shell mussel (Anodonta imbecillis)

Distinguishing features: The shell is nearly paper-thin, elongate, up to 65 mm long, higher towards the posterior end. Internally there are no hinge-teeth.

Scale 20 mm

Other descriptive details: The beaks are flattened and do not project above the dorsal margin. In dorsal view the beak sculpture appears as faintly double-looped concentric ridges.

Distribution: Southern Great Lakes region through the Mississippi Valley to the Gulf Coast; westward to central Kansas and southwest- ward through Texas to Rio Conchos, Chihuahua; eastward to northern Florida, and on the Atlantic coast from Maryland to Georgia. The one population in New Mexico, in Conchas Reservoir, San Miguel County, is hundreds of miles from the nearest occurrences in eastern Kansas, Oklahoma, or south Texas.

Biology: Anodonta imbecillis is more widely distributed than most other species of freshwater mussels in North America. Significant features of its biology that are probably responsible for this wide range include hermaphroditism, ability to develop without metamorphosis on a fish host, and wide variety of larval hosts when these are used. Van der Schalie (1970) classified the present species as dominantly hermaphroditic, but suggested there may be latitudinal variation in this feature. He cited Anodonta henrvana as not hermaphroditic on the basis of preliminary examination; that form (described from the lower Rio Grande drainage) is considered here as a synonym of A. imbecillis.There is thus support for the suggested variation in sexualit Practically all freshwater mussels pass a parasitic larval life on one or several kinds of freshwater fishes, before metamorphosing to adults. Howard (1914) found post-larval juveniles within parent mussels in southern Illinois, and concluded that non-parasitic development was usual. Nevertheless, later studies have revealed a larval parasitic stage. Tucker (1927) described and illustrated the gloch- JD-40

idium and its larval developement on green sunfish, Lepomis cvanellus Rafinesque. Subsequent studies (Trdan and Hoeh 1982, and references therein) have revealed an additional seven species of fish may serve as host, at least in the laboratory. The number of studies remains so few that the relative importance of parasitism or non-parasitic development remains uncertain, as is the possible effect of environmental variation on this development.

The substratum types in which this species has reportedly been found range from mud and sand to gravel in lakes and rivers. The New Mexico occurrences in Conchas Reservoir are shells drifted along shore, and might have come some distance as shells buoyed up by gas inside.

Status: Only one small population is known living in New Mexico, represented by rare fresh shells.

Theoretically there is a possibility that the population in Conchas Reservoir could have been introduced artificially. But modern shells (probably several decades old) from the Conchas River upstream, at Variadero, indicate a former river population there. This is interpreted as the source of the reservoir stock.

Conservation: Entrenchment of the channel of the Conchas River has greatly altered local habitats in the stream. Both the Pond-horn mussel (Uniomerus tetralasmus) and Paper-shell mussel formerly lived in the Conchas, but are now extinct. The rare specimens of Anodonta found in Conchas Reservoir indicate a marginal population whose future survival is in doubt. JD-49

Berlandier's mussel (Cyrtonaias berlandieri)

Distinguishing features: This freshwater mussel may attain a length of 140 mm (5 1/2 inches). The thick and solid shell is quadrangular-ovate in outline, with smooth rounded beaks. The outer surface is smooth except for lines of growth; faint radial color markings may be present. Inside, the right valve bears a long narrow lateral tooth (L), and a massive blunt pseudocardinal tooth (P). These fit into grooves between the corresponding teeth, double in the left valve. Interior of the shell is a deep, rich purple.

••••■•■•...■ .■■■• J D - 50

Distribution: Mouth of the Pecos River and Lower Rio Grande northeastward to the Trinity River, Texas. The population in the Pecos River near Carlsbad, Eddy County, New Mexico, may have been isolated from the occurrences in the lower Pecos River of Texas.

Biology:. No studies of life history or ecology have been carried out. For general remarks see under Pope's mussel, Popenaias popei.

Status: Listing of this species in the modern fauna of New Mexico rests on a fragmentary valve found along the Pecos River below Carlsbad. As the shells of this species are massive and could survive flood transport for some distance, it appears unlikely a living population survives.

Remarks: Some authors combine this species with Cyrtonaias tamnicoensis of northeastern Mexico. Whether the two forms are separate species, or subspecies, or merely a single form will require further study. - J 0 51

Pope's mussel (Popenaias popei)

Distinguishing features: This freshwater mussel may attain a length of 100 mm (4 inches). The solid shell is elongate in outline, roughly rectangular with rounded corners. The outer surface is smooth except for lines of growth. Inside the right valve bears a long narrow lateral tooth (L) and a blunt pseudocardinal tooth (P). These fit into grooves between the corresponding teeth, doubled in the left ' valve.

1ft". ; ••

Other descriptive details: The thin external periostracum is dark brown, and ordinarily worn off at the beaks to some extent, exposing the mother-of-pearl like shell. Juvenile shells show beak sculpture of small tubercles.

Distribution: Lower Pecos River and tributaries of the lower Rio Grande, Texas and Mexico, southward to the Rio Panuco drainage in San Luis Potosi. New Mexico: Pecos River and adjacent lower courses of artesian spring=nd streams in the vicinity of Roswell and Carls- bad, Chaves and Eddy Counties.

Biology: No studies of life history or ecology have been carried out. Like other freshwater mussels, this is a filter-feeder, strain- ing suspended organic particles from the water it pumps through its gills. Life span (estimated from growth rings on the shell) is likely to reach 10 years. Like other freshwater mussels, the life history is presumed to include a larval stage parasitic on one or more species of fish. The distribution of this mussel is unlike any other, hence it may be determined partly by the necessary fish hosts JD-52

(unknown).

Status: The former range(both total, and in New Mexico) is now greatly reduced on account of dam construction, pollution, or groundwater development. Shells from recently living animals have been found in New Mexico only during the early part of the century, in the North Spring River at Roswell, Chaves County, and in the lower Black River near Carlsbad, Eddy County. Fresh empty shells are not uncommon along the Pecos River near Carlsbad, and, perhaps the clams are still living in relatively inaccessible situations.

Conservation: The mussels anywhere are subject to all the hazards of toxic substances added upstream, from pesticides or oil-field wastes to municipal pollution, as well as to the reduction in flow caused by groundwater development. In addition, elimination or merely rarity of the essential fish host(s) could break the life cycle without killing any adults. Transplanting a stock to protected habitat would be futile with no suitable fish host for larvae. An early priority should be studies to determine the species and age-range of suitable fish hosts.

Remarks: Prognosis for the survival of this species, the largest mollusk in the state, is poor. JD-53

Pond-horn mussel (Uniomerus tetralasmus)

Distinguishing features: The shell is elongate-rhomboid, up to four inches long, with beaks at more than one-fourth the shell length from the anterior end, externally smoothly rounded with no angular ridge. Internally the left valve has two lamellar lateral teeth and two pseudocardinal teeth; the right valve contains one of each.

Other descriptive details: The beaks are prominent, with sculpture of fine wrinkles.

Distribution: South-central and southeastern United States; westward as far as the Arkansas and Cimarron River drainages, southeastern Colorado and northeastern New Mexico, and the lower Rio Grande drainage, Texas and Mexico. In New Mexico there are no living occurrences known, but the species is to be expected in the Dry Cimarron tributaries in the northeastern corner of the state. Shells from the Conchas River, San Misuel County, are several decades old and the Species probably no longer lives in that river.

Biology: This is one of the few freshwater mussels that can survive drying of its habitat. It is the most resistant to drought of any mussel in North America, capable of surviving for months buried in the mud bottom of a dry pond. Hibbard and Taylor (1960) quote an account of Uniomerus surviving packed in a dry box for 38 days, all reviving and becoming active within a few minutes when returned to water.

Status: The species has been greatly restricted and is perhaps even extinct in the westernmost part of its range, in Colorado and New Mexico. Brandauer and Wu (1978) recorded only three localities in Colorado, with no certainty the species still lives in the state. In New Mexico specimens from archeological sites indicate Indians found this mussel living where none are found today. Such records are those from the Hodges site on Plaza Larga Creek 8 miles south- JD-54

east of Tucumcari, Quay County, dated from the late 14th or early 15th to middle 16th century (Dick, 1953); and from a rock shelter in the Dry Cimarron valley in Union County (Renaud, 1930). J D-55

Striate pea-clam (Sphaerium striatinum)

Distinguishing features: The shell attains a length of up to 12 mm, with external sculpture of concentric riblets. In dorsal view the beaks are outlined by a series of low, wide riblets; these become narrower and more irregular over the rest of the shell surface.

Scale 2 NUN

Other descriptive details: The hinge-plate is wide, broadly and evenly curved. The ventral margin is broadly curved, and greatest shell length is distinctly below mid-height. The lateral teeth are stout, single in the left valve, double in the right valve.

Distribution: Widespread in northern North America except for the extreme southwest; as far south as the Rio Grande drainage in South Texas and northeastern Mexico. In New Mexico restricted_ to four narrowly localized populations: in the Rio San Jose near McCartys Valencia County; upper Conchas River, San Miguel County; and the upper Dry Cimarron and North Canadian Rivers in Union County.

Biology: Foster (1932) studied the life history of the present species (reported as S. solidulum)in Illinois. Individuals are hermaphroditic, producing two broods of young during the life span of a year. Maximum reproduction occurs in the winter, whether or not the parent is of the summer-brood or winter-brood. In contrast, Heard (1977) found that most births in the River Raisin, southeastern Mich- igan, were in summer; but he emphasized that not only is there intra- specific variation in species, also environmental effects may influ- ence or even regulate fertilization, development, and birth. Substratum preference was studied by Gale (1973) in Oklahoma. Adults ahowed no clear preference for mud, sand, or sandy mud, but juveniles preferred mud. The question remains open whether there are correlated factors, such as oxygen availability or food, that determine the occurrence of the clams in a given substratum. Collec- tions in New Mexico have been from mud, silt, and sand. The data provided by Gale (1973) indicate that both fish predation, and competitive interactions (of unknown type) with Musculium transversum may be more important than substratum type in determining distribution in a stream. Both species occur in perennial creeks and rivers where the bottom is stable, but where one species is abundant the other is absent or usually scarce. In New Mexico the three larger populations of Sphaerium striatinum (Rio San Jose, Dry Cimarron and North Canadian Rivers) are not associated with Musculium; in the Conchas River, Musculium transversum is more abundant than Sphaerium striatinum.

Effects of sewage pollution on Sphaerium striatinum were studied in Ohio by Ingram et al. (1953, as S. solidulum). A slight amount of domestic sewage fertilized the stream and increased the abundance of clams, presumably by increasing their food supply. At and below a primary sewage treatment outflow Sphaerium was completely absent to the mouth of the stream, 7.3 miles distant.

Morphology of this species was described by Monk (1928, as Sphaerium notatum).

Status: Fossils indicate the species was formerly more widespread in the state. Climatic changes toward more arid climate, and intense storms that cause scouring of the stream bed, are probable causes of the reduction in range. At present the species is narrowly restricted to four local populations.

Conservation: Degradation of streams through overgrazing in the northeastern part of the state, or pollution of the Rio San Joe by mining wastes or municipal sources, are the principal threats.

Remarks: To the south and west, in Mexico and Arizona, Sphaerium striatinum is replaced by its near relative, S. trianqulare (Say). J 0-57

Raymond's pea-clam (musculium ravmondi)

Distincuishinq features: The shell reaches a length of about 5 mm, with external sculpture of very fine raised threads. The embryonic shell is set off by a constriction, forming a conspicuous cap oblique to the greatest length. The outline in side view is subcircular, with strongly curved outline.

Scale 1 mm

Other descriptive details: The shell is nearly paper-thin, with narrow, lamellar lateral teeth, single in the left valve, double in the right. In dorsal view the shell may appear almost spherical.

Distribution: Northern North America from Alaska south to the northern United States, at higher elevations southward in the Sierra Nev- ada, California, and in the Rocky Mountains to southern Utah and northern New Mexico. The single population known in New Mexico is in the Sangre de Cristo Mountains, in Colfax County.

Biolocv: The species is found most often in ponds and lakes in a muddy bottom, sometimes even in seasonal waters, but occurs also in streams. It is common in glacial lakes and ponds in Colorado. The population in New Mexico, the southernmost occurrence, is in a marshy area subject to wide seasonal variation in flow of water. No studies of life history or biology have been carried out.

Status: The one known population is at the southern limit of range. Few if any additional occurrences in the state are expected, as marshy situations at high elevations are a rare habitat.

Conservation: The population is within private land maintained for recreational use. Potential threats include pesticides, mosquito- abatement measures, and local land or road improvements. JD-58

Remarks: The species most likely to be confused with this is Musculium truncatum. From that form it differs by its more inflated shell, with more strongly curved outline. In young shells the anterior end is rounded, unlike the truncate end of juvenile • truncatum. An antero-dorsal angle may be present in truncatum, but not in ravmondi. The shell of truncatum in dorsal view is less inflated than that of ravmondi. JD-59

Circular pea-clam (Musculium Partumeium)

Distincuishino features: The shell reaches a length of 10 mm: with length and height nearly equal, and the posterior end higher than the anterior. The posterior end is broadly curved, and nearly at right angles to the broadly curved dorsal margin.

Scale 2 mm

Other descriptive details: The shell is thicker than in other species of the genus, with a wide hinge. The embryonic shell may be set off from the later shell by a weak incised line. External sculpture consists of very fine raised threads. The lateral teeth are narrow, single in the left valve, double in the right.

Distribution: Southernmost Canada and United States east of the Rocky Mountains, south to Nuevo Leon, Mexico. The one locality in New Mexico, in a tributary of the Dry Cimarron River, Union County, is the westernmost population known.

Bioloory: Ostensibly there are several publications dealing with laboratory growth, reproductive biology, and life history of this species. At least some refer to Musculium truncatum (for discussion see under that species). Whether the study by Way et al. (1980) pertains to Partumeium or truncatum remains uncertain. In south Texas and New Mexico the habitat is perennial creeks and sloughs.

Status: Only one population is known, at the northeastern edge of the state.

Conservation: The population is stable under present conditions of land use (stock raising), but it is small and marginal.

Remarks: This is the only species of Musculium in which there is significant geographic variation, perhaps an indication that further study is needed. Shells in the southern part of the range (New Mexico, Texas, Oklahoma) attain a larger size than those in the north, with thicker JD-60

shells and wider hinge. Here they are obviously distinct from M. truncatum, in these as well as other features. In the thinner, more northern specimens M. partumeium differs by the more regularly curved ventral and anterior margins, and by the hinge being oblique to the line of greatest shell length. Specimens identified by Herrington (1962) as M. partumeium from California, Nevada, and Mon- tana I believe are M. truncatum. So far as known M. partumeium is not found west of the Great Plains. J D-61

Wide pea-clam (Musculium transversum)

Distinauishina features: The shell reaches a length of 12 mm, with the length distinctly greater than the height, and the posterior end higher than the anterior. The beaks are low, nearer the anterior end, and may be set off by a weak constriction.

Scale 2 mm

Other descriptive details: In side view internally the hinge shows a generally broad curve, but with an inflection just behind the cardinal teeth. The shell is thin, with external sculpture of raised threads. The lateral teeth are narrow, single in the left valve, double in the right.

Distribution: Much of North America, generally east of the Rocky Mountains; from central Canada south onto the Plateau of Mexico, and in northwestern Mexico and southern Arizona. In New Mexico formerly in the lower Pecos River, Eddy County, now extinct. Only two populations are known to survive: a marginal population in the middle Conchas River, San Miguel County, and a larger one in a tributary of the Dry Cimarron River, Union County.

Hioloav: Aspects of life history and habitat preference of this species have been studied by Gale (1971, 1972, 1977; Gale and Lowe, 1971). In laboratory experiments the clams preferred mud substratum to sandy mud or sand. In both field (Iowa) and laboratory experiments the occurrence of the capped beak set off from the definitive shell was found variable; it is evidently due to a pause in growth immedi- ately after birth and may be influenced by a variety of factors. Growth of the clams may be relatively rapid for the family, with the life cycle completed in about a month. Food is phytoplankton, ingest- ed with little or no selectton, including both diatoms, blue-green and green algae. In winter, when water temperatures fall to 20-40 C., feeding practically ceases.

Musculium transversum grows rapidly and also produces more young than other species of the genus, in the older, more fecund individuals. Gale (1977) recorded 86 embryos in a specimen from the Mississippi River, Iowa; and Heard (1977) found up to 70 in the oldest adults from Kansas. JD-62

Unlike all other species of the genus, Musculium transversum is restricted to perennial streams.

Status: The major population of this species in the state has been eradicated. Formerly Musculium transversum was abundant in the Pecos River below Carlsbad, Eddy County. Presumably diversion of waters for irrigation development is responsible. The remaining populations are small, the one in Conchas River marginal.

Conservation: The population in Conchas River is subject to the hazards of flood scour and any potential development upstream that might bring pollution or alteration to the habitat. The population in the Dry Cimarron tributary is stable under present conditions of land use (stock raising), but small.

Remarks:- Some specimens of Musculium transversum and M. partumeium may be confused. Distinctive features of transversum are coarser sculpture, less curved ventral margin, a posterior margin not at right angles to the dorsal margin, and an inflection of the hinge. JD-6;

Truncate pea-clam (Musculium truncatum)

Distinguishing features: The shell attains a length of about 10 mm, with external sculpture of very fine raised threads. The embryonic shell is usually set off by a constriction to form a low but distinct cap, normal to the straight dorsal margin. The outline in side view is roughly oval to subquadrate, with a broadly curved ventral margin, more sharply curved anterior margin, and nearly straight to broadly curved posterior margin that joins the ventral margin with narrower curve or even subangulation.

Scale 2 mm

Other descriptive details: The shell is nearly paper-thin, with narrow, lamellar lateral teeth, single in the left valve, double in the right.

Distribution: Most of North America from Alaska south to southern California and Florida, but absent in the arid Southwest. In New Mexico only one population is known, in Clayton Lake, Union County.

Biology: Seasonal life history was studied in ponds in southeastern Michigan by Kenk (1949) and Thomas (1963; as partumeium). In both permanent and temporary ponds the clams live about one year; adults die at the onset of winter, the young surviving in either water or dry soil to begin growth in spring.

Some of the data provided by Heard (1977) for Musculium partumeium evidently are based on M. truncatum, as he cited the locality where Kenk (1949) studied the species. Whether all of his specimens were M. truncatum, or also partly partumeium, remains an open question. The data on M. lacustre quoted by Heard refer to the Eurasian species: his original data from American specimens to M. truncatum. The data on reproductive biology of the species evidently need review in the light of revised taxonomy. JD-64

The habitats in which Musculium truncatum has been collected in western North America range from perennial lakes and slow rivers to marshes and seasonal ponds. In general, it is replaced in high-altitude ponds by M. ravmondi, although M. truncatum is found also in mountains locally in larger marshes, lakes, or low- gradient rivers. The one locality in New Mexico is Clayton Lake, on the northeastern plains.

Status: Known from only one population in the state.

Remarks: Review of specimens and literature has revealed taxonomic confusion of several species of Musculium, so that doubt is cast on just what species and how many are involved in biological and morphological studies. Correspondence between the classification by Herrington, the latest reviser of the group, and that used herein for the species in question is as follows:

Herrington (1962) Present classification partumeium and some lacustre Partumeium lacustre form rvckholti in part ravmondi lacustre (typical) and form ryckholti in part; some partumeium truncatum

Part of the difference in these classifications is due to different opinions as to species rank, part to different identifications of the same specimens. So far as previous literature is concerned, the most prolific source of confusion has been the allocation of truncatum as a synonym of partumeium by Herrington. The present usage is consistent with that of earlier authors such as Baker (1928), and with the description and illustration by Prime (1865) who based his description upon the type specimens and distinguished the species clearly from partumeium.

From examination of specimens I support the opinion by Ellis (1962) that Musculium lacustre is Eurasian, and that its variety rvckholti does not occur in North America. The oldest names clearly applicable are truncatum and ravmondi.

Distinctions between truncatum, partumeium, and raymondi are summar- ized under those two species. JD-65

Lillejeborg's pea-clam (Pisidium lillieborqi)

ingniqhing foatilroQ• The shell is subcircular in side view, with broad swollen beaks projecting strongly above the dorsal margin. A weak angle 'separates the dorsal margin from the anterior slope. Surface sculpture consists of fine to coarse raised threads. Shell length may attain 4.5 mm.

Aul

Scale 1 mm JD-66

Other descriptive details: The posterior outline approaches a quarter- circle. Shell texture is dull to slightly glossy, the color tan to 'brown. In some specimens the beaks are bordered by low ridges parallel to the threads of the later shell. Posterior lateral teeth PI and PIII are straight and converge toward the beaks.

Distribution: Circumboreal. In North America from the Arctic south to the northernmost United States from coast to coast, and southward at high elevations to northern California (Trinity Alps), Utah (Uinta Mts.); and northern New Mexico (Sangre de Cristo Mts.). The one population known in New Mexico is from Nambe Lake, Santa Fe County.

Biology: The species is especially characteristic of lakes. Both in Europe and North America it is a northern and alpine species.

In Lake Titisee, Germany, Meier-Brook (1969, 1970) studied substratum preferences and life history of Pisidium. P. lillieborgi prefers fine- grained (less than 0.5 mm) organic sediment, in which it forms a burrow beneath the surface. Nutrient-bearing and oxygenated water is pumped through the overlying interstices of the sediment and out into the burrow. Food is presumably fine organic particles collected and sorted in the slit of the foot, morphologically ventral but directed upward in the normal life position. Young are born in later July and in August, at a length of 1-1.2 mm. They grow in a pre-reproductive period for 20-21 months, then mature se, ually as simultaneous hermaphrodites. About four eggs develop in brood pouches in the gills, and after 21/2 - 31/2 months the young are born. Adults may live three or four years, with an annual reproductive period and increased number of young in a brood (maximum observed, 13).

Status: The species is stable under present conditions in Nambe Lake.

Remarks: The population in Nambe Lake is the only one known in New Mex- ico, and may be widely disjunct from other occurrences.

Other high mountain lakes have been sampled in the San Juan and Sangre c Cristo Mountains without finding the species. There is thus a suggestiox frc that occurrence in the Sangre de Cristo range may be widely disjunct , the neareast populations. This is in keeping with the unexpected disco ery of a new species, the Sangre de Cristo pea-clam, in these mountains and emphasizes the biological distinctiveness of the area. 0 1 Nambe Lake (35 48 1" N. Lat., 105°46'43" W. Long.; 11,365 feet/3465m elevation) appears to be both the southernmost locality known in either North America or Eurasia, and also the highest elevation. The maximum elevation recorded for Europe by Ellis (1962) is 2300 m in the Alps. Dance (1970) cited a range of 5500 to 7500 feet in the Pyrenees, where it is "common in many mountain lakes".

From the known European occurrences, Pisidium lillieborg might be expec- ed in many lakes in the Rocky Mountains. Yet this seems not to be the case. Only two areas of glacial lakes have been collected carefully for Pisidium, Grand Mesa and the mountains west of Boulder, both in Colorado. Henderson (1924) recorded a variety of species, but not the JD-67 present one; hence there are grounds for supposing theSangre de Cristo population may be far isolated. The sporadic occurrence of this species in the Rocky Mountains, in contrast to others found more widely, leads to the inference that passive dispersion is rare or non-existent. This is in agreement with Heard (1962), who believed that "the distribution of sphaeriids was originally accomplished by active migration through confluent drainage patterns". Thus the southern occurrences at high elevations would seem to be not only far removed from one another, but long isolated. Meld's pea-clam (Pisidium milium)

Distincuishinc features: The shell is ovate-quadrangular to rhom- boidal in side view except for the prominent backward-pointing broad beaks, strongly convex in dorsal view view, and up to 2.8 mm long. The outer surface has a glossy texture, and sculpture of numerous irregular fine raised threads. or narrow bands. The hinge is less than three-fourths of total shell length, narrower below the beaks. All cardinal teeth are thin and lamellar: C2 and C4 slender, not quite parallel; C3 weakly curved and slightly wider posteriorly. These cardinals are closer to the anterior lateral teeth (AI-AIII) than to the posterior (PI-III ).

Scale 1 mm

Other descriptive details: Greatest shell length is below the horizontal mid-line. Surface color amber to yellowish-gray. Inner lateral teeth lamellar. Adductor muscle scars (m) relatively low, the posterior scar below the horizontal mid-line. Embryonic shell may be bordered by 3-5 raised threads or narrow bands, strong- er than the sculpture over the rest of the shell. Tip of anterior end low.

Distribution: Circumboreal. Widespread in northern North America; southward in the Rocky Mountains at higher elevations to northern New Mexico. Known from four populations in New Mexico, three in the San Juan Mountains, Rio Arriba County, and one in the southern Sangre de Cristo Mountains, Colfax County. JD-69

Bioloav: Pisidium milium is found in ponds, lakes and slow perennial streams, usually in a mud bottom. Despite its wide geographic range, it is one of the least variable species of the genus. The localities in New Mexico are the southernmost known in North America, and close to the highest elevations. Meier-Brook (1970) found that in Lake Ursee, Germany, the species has a single reproductive period per year, from early spring until late summer or fall.

Remarks: Pisidium milium is most likely to be confused with the more widespread P. contortum Prime. The latter species differs as follows: The outline in side view is more nearly oval, with a more curved ventral margin, anterior end more broadly rounded and not so low, and dorsal-anterior margin less curved. The beaks are less prominent, and do not incline backwards. The muscle scars are not so low, the posterior adductor scars being transected by the horizontal mid-line. In dorsal and end views the shell is less convex. The hinge is both longer and wider. Like that of P. milium it is narrow below the beaks, but this narrow interval between the lateral teeth is longer. JD-70

Wide-hinged pea-clam (Pisidium pauperculum)

Distinguishing features: The shell is ovate-triangular in side view, with smooth broad beaks, strongly convex in dorsal view, up to 2.75 mm long. The outer surface is glossy, with numerous fine growth lines. The hinge-plate is more than three-fourths the total shell length, and massive. In the right valve the third cardinal tooth (C3) is long and narrow, slightly expanded at the posterior end. The first anterior (Al) and first posterior (PI) lateral teeth are strong and massive; PIII and AIII relatively weak. In the left valve, both laterals are high and massive, the cusp (c) of PII central, that of All distal or central.

Scale 1 mm

Other descriptive details: The cardinal teeth are located midway between the laterals, and small relative to the broad hinge-plate. C2 and C4 are narrow pegs. The ligament pit (LP) is short and broad, about half the width of the hinge-plate. Shell color varies from lemon-yellow to tan.

Distribution: Widespread in southern Canada and the United States, but rare and sporadic in the arid and semi-arid Southwest. New Mexico: only one locality known, Ojo del Gallo, San Rafael, Cibola County, where now extinct.

Biology: No studies of life history have been made. The species is found characteristically in lakes and relatively swift creeks J D- 71 and rivers, thus in perennial waters not subject to significant seasonal variation. The one specimen collected at San Rafael may have come from the stream fed by the spring.

Status: Extinct in New Mexico.

Conservation: See under Promenetus exacuous. JD-72

Singley's pea-clam (Pisidium singleyi)

Distinguishing features: The shell is ovate in side view except for the prominent broad beaks, strongly convex in dorsal view, up to 2.5 mm long. The outer surface has a silky texture from the sculpture of numerous fine raised threads. The hinge-plate is more than three-fourths the total shell length, and narrow in the middle. The second cardinal tooth (C2) projects obviously into the cavity of the valves, and the base of C3 less so. In the right valve, the first anterior lateral tooth (Al) is developed strongly and• expands into the cavity of the valves; AIII is so weak as to be hardly visible; PI and PIII are equally high but PI is longer. In the left valve, All and PII are strong, with cusps (c) on their distal halves.

Scale 1 mm Other descriptive details: The cardinal teeth are obviously closer to the anterior laterals than to the posterior laterals. C2 is a strong peg-like tooth, C4 a weak, straight lamella. C3 is curved, with a broad, short posterior limb hnd a narrow anterior limb about three times as long as the posterior limb. The ligament pit (LP) is long and narrow. The shell is usually pale tan in appearance, but often covered by organic growth.

Distribution: Southernmost United States southward through Central America and Greater Antilles. New Mexico: Blue Spring and Geyser Spring, Eddy County, and spring near former Fort Harmony, Socorro County.

Biology: No studies of life history or ecology have been made. In southern Texas and Mexico this tiny clam is found in a variety of habitats, from springs to creeks and rivers, but northward its habitat range is restricted and the extreme localities are in thermal springs. Hence winter minimum temperatures are probably a factor in its northern limit of distribution. Perennial flowing water, fine mud substratum, and protection from flood scour are JD- 73

other habitat requirements. Like species studied by Meier-Brook (1969), P. singleyi presumably lives just below the surface in fine organic sediment, inhaling oxygenated water through the overlying sediment and discharging feces with the exhalant current into the open "burrowing canal". Food is presumably fine organic particles sorted and carried by cilia in the slit on the foot, morphologically ventral but upwards in the normal life position.

Status: The colony near former Fort Harmony is a small one, occurring in one of the smaller spring outflows and not in the large sources that support populations of Tryonia. The other two colonies are larger.. Even minor development of one spring outflow near Fort Harmony could eliminate the colony there.

Conservation: The populations of the species are stable under present conditions. Preservation of Blue Spring will protect the species there. Even minor development of one spring outflow near Fort Harmony could eliminate that colony. Potential threats to the latter include capping the spring, impoundment, or drawing down the water table by pumping; none of these appear likely in the immediate future. Current land use is for stock grazing, and this is compatible with maintenance of the species.

Remarks: This is a principally tropical to subtropical species . at the northern margin of its range. The known populations in New Mexico are presumably able to survive in the outflow of springs that insulate them from low winter temperatures. J D- 7it

Globular pea-clam (Pisidium ventricosum)

Distinguishing features: The shell is tiny, up io 2.2 mm long, broadly ovate in side view except for the prominent swollen beaks, and almost spherical in dorsal view. The outer suface is glossy. The hinge is less than three-fourths of total shell length, with short, stout second anterior (All) and posterior (PI4 lateral teeth. In the right valve the posterior laterals (PI, Pill) are joined by a pseudocallus (ps).

Scale 1 mm Jo-75

Other descriptive details: The ligament pit (LP) is short. C3 is broad at the posterior end, and may protrude into the cavity of the shell. A III is weak and inconspicuous. Cusps (c) of the lateral teeth are subcentral, that of Pill being obliterated by the crest of the pseudocallus (ps).

Distribution: Northern North America, from the Arctic south to the northern United States, and southward at higher elevations to southern California (San Bernardino Mountains), central Utah (Fish Lake Plateau) and northern New Mexico (Sangre de Cristo Mountains): The two populations known in New Mexico are in Nambe Lake and Santa Fe Lake, Santa Fe County.

Biology: This tiny clam lives in rivers and lakes, but most usually in ponds. It is common in the glacial lakes of Colorado at high elevations. The occurrences in New Mexico are at the highest elevations known for the species, and, in the Rocky Mountains,.the southernmost.

No studies of life history or ecology have been made. In Nambe Lake it was rare in the mud bottom along with abundant Pisidium lillIeborgi, and in Santa Fe Lake likewise rare in mud bottom with more common P. contortum and B. variabile.

Status: The species is rare at both the known localities. Only four specimens out of thousands of 2.ts_islium were found in Nambe Lake, and only two out of hundreds of others in Santa Fe Lake.

Conservation: Both populations are stable under present conditions, and protected by being in the Santa Fe watershed or in National For- est Land.

Remarks: By analogy with the number of localities known in Coloz:ado, other occurrences of the species may be expected in the Sangre de Cristo Mountains. JD-76

Sangre de Cristo pea-clam (Pisidium a)

Distinguishing features: The shell is ovate to ovate-quandrangular in side view except for the prominent broad beaks, strongly convex to globose in dorsal view, and up to 3.2 mm long. The outer surface has a silky texture, and sculpture of broad, smooth riblets that set off the smooth beaks. The hinge is less than three-fourths of total shell length, and narrow. All cardinal teeth are thin and lamellar: C2 and C4 short, not quite parallel; C3 weakly curved and slightly wider posteriorly. These cardinals are closer to the anterior lateral teeth than to the posterior. The ligament pit (LP) is short, relatively wide, 60-80 percent of the hinge-plate width. •

Scale 1 mm J 0-77

Other descr4tive details: Greatest shell length is below the horizontal mid-line. Surface color yellowish-gray. Second lateral teeth (All and PII ) strong and high; cusp (c) of All central, of PII distal. Al and PI strong, AIII and PIII low, all with central cusps. PI and PIII barely converge. Muscle scars of anteridr and posterior adductors (m) below the horizontal midline.

Distribution: Middle Fork Lake, 10,845 ft. elevation, at head of Middle Fork of Red River, Taos County, in the Sangre de Cristo Mountains.

Biology: No studies oflife history or ecology have been made. The species has been found only at the type locality even though other glacial lakes in the Sangre de Cristo Mountains have been sampled. In Middle Fork Lake it was found in fine mud at the margin of the lake as well as in the outflow.

Status: The species is common in Middle Fork Lake, but so far known only from the one population.

Conservation: Middle Fork Lake is within National Forest land, and accessible only on foot or by some four-wheel-drive vehicles. The area is used only for recreation, and present limited use is compatible with stability of the species. The only modification of the lake thus far has been construction of a small earth dam to stabilize the outlet. Potential threats include pesticide poisoning, or any poisoning of the lake for management of fishery.

Remarks: The genus Pisidium is found world-wide, and most species are found on much of a given continent, or on more than one continent This is the most narrowly localized Pisidium in North America, even if it should be found elsewhere in the Sangre de Cristo Mountains. From the known fossil record of Pisidium, a history of isolation and evolution over several million years at least is implied for the Sangre de Cristo pea-clam. JD-78

LITERATURE CITED

Mollusks

Anderson, Sydney. 1961. A relict population of Microtus pennsvlvanicus in southwestern New Mexico. Amer. Mus. Novit. 2034: 1-3.

Bailey, Vernon. 1931. Mammals of the southwestern United States with special reference to New Mexico. N. Amer. Fauna 53: 1-412.

Baker, F. C. 1928. The fresh water Mollusca of Wisconsin. Wisc. Geol. Nat. Hist. Survey Bull. 70, 2 vols. ---- 1945. The molluscan family Planorbidae. Urbana, Univ. Illinois. 530 pp. Brandauer, Nancy, and S.-K. Wu. 1978. The Bivalvia of Col- orado, Part 2, The freshwater mussels (Family Unionidae). Nat. Hist. Invent. Colo. 2: 41-60. Burky, A. J. 1971. Biomass turnover, respiration, and interpopulation variation in the stream limpet Ferrissia rivularis (Say). Ecol. Monogr. 41: 235-251.

Clarke, A. H. 1973. The freshwater molluscs of the Canadian Interior Basin. Malacologia 13: 1-509.

Dance, S. P. 1970- Pisidium lillieboraii Clessin, in the River Teifi, west Wales. Jour. Conchol. 27: 177-181. . Dick, H. W. 1953. Two rock shelters near Tucumcari, New Mexico. Bur. Amer. Ethnol. Bull. 154: 267-284.

Ellis, A. E. 1962. British freshwater bivalve molluscs. Linn. Soc. London, Synops. Brit. Fauna, 13: 1-92. Foster, T. D. 1932. Observations on the life history of a fingernail shell of the genus Sphaerium. Jour. Morphol. 53: 473-497.

Gale, W. F. 1971. An experiment to determine substate preference of the fingernail clam, Sphaerium transversum (Say). Ecology 52: 367-370. 1972. Seasonal variability in calyculism in Sphaerium trans_ versum (Say). Nautilus 86: 20-22. ---- 1973. Substrate preference of the fingernail clam, Sphaerium striatinum (Lamarck) (Sphaeriidae). SW Nat. 18: 31-37. ---- 1977. Growth of the fingernail clam, Sphaerium transversum (Say), in field and laboratory experiments. Nautilus 91: 8-12. J D- 79

---- and R. L. Lowe. 1971. Phytoplankton ingestion by the fingernail clam, Sphaerium transversum (Say), in Pool 19, Mississippi River. Ecology 52: 507-513. Gilmore, R. J. 1917. Notes on reproduction and growth in certain viviparous mussels of the family Sphaeriidae. Nautilus 31: 16-30.

Gordon, E. D. 1961. Geology and ground-water resources of the Grants-Bluewater area, Valencia County, New Mexico. N. Mex. State Engineer Tech. Rept. 20: 1-109.

Heard, W. H. 1962. Distribution of Sphaeriidae (Pelecypoda) in Michigan, U. S. A. Malacologia 1: 139-160. ---- 1977. Reproduction of fingernail clams (Sphaeriidae: Sphaerium and Musculium). Malacologia 16: 421-455. Henderson, Junius. 1924. Mollusca of Colorado, Utah, Montana, Idaho and Wyoming. Univ. Colo. Studies 13: 65-223.

Herrington, H. B. 1962. A revision of the Sphaeriidae of North America (Mollusca: Pelecypoda). Misc. Pubs. Mus. Zool. Univ. Mich. 118: 1-74. Hibbard, C. W. and Rinker, G. C. 1942. A new bog-lemming (Svnaptomvs) from Meade County, Kansas. Univ. Kans. Sci. Bull. 28: 25-35.

Howard, A. D. 1914. A second case of metamorphosis without parasitism in the Unionidae. Science 40: 353-355.

Ingram, W. M., et al. 1953. Relationship of Sphaerium solidulum Prime to organic pollution. Ohio Jour. Sci: 53: 230-235. Kenk, Roman. 1949. The animal life of temporary and permanent ponds in southern Michigan. Misc. Pubs. Mus. Zool. Univ. Mich. 71: 1-66, pl. 1-3.

Meier-Brook, C. 1969. Substrate relations in some Pisidium species (Eulamellibranchiata: Sphaeriidae). Malacologia 9: 121-125. ---- 1970. Untersuchungen zur Biologie einiger Pisidium-Arten. Arch. Hydrobiol. Suppl. 38: 73-150.

Monk, C. R. 1928. The anatomy and life-history of a fresh-water mollusk of the genus Sphaerium. Jour. Morphol. Physiol. 45: 473-503. J D- 3o

Mozley, Alan. 1932. A biological study of a temporary pond in western Canada. Amer. Nat. 66: 235-249.

1=0 MII• 100- 1936. The statistical analysis of the distribution of pond molluscs in western Canada. Amer. Nat. 70: 237-244. Noel, M. S. 1954. Animal ecology of a New Mexico springbook. Hydrobiologia 6: 120-135.

Pip, Eva, and Paulishyn, W. F. 1971. The ecology and distribution of Promenetus exacuous Say (Gastropoda: Planorbidae) in southern Manitoba. Can. J. Zool. 49: 367-372. Prime, Temple. 1865. Monograph of American Corbiculidae. Smithson. Misc. Coll. 145: 1-80.

Renaud, E. B. 1930. Prehistoric cultures of the Cimarron Valley, northeastern New Mexico and western Oklahoma. Colo. Sci.Soc. Proc. 12: 113-150.

Russell-Hunter, W. D. 1978. Ecology of freshwater pulmonates. In Fretter, V. and Peake, J. (eds.), Pulmonates, vol. 2A, Systematics, evolution and ecology, pp. 335-383. Academic Press.

---- et al. 1967. Interpopulation variations in calcium metabolism in the stream limpet, Ferrissia rivularis (Say). Science 155: 338-340.

---- et al. 1970. Interpopulation variation in shell components in the stream limpet, Ferrissia rivularis *(abstract). Biol. Bull. 139: 402.

Summers, W. K. 1976. Catalog of thermal waters-in New Mexico. N. Mex. Bur. Mines & Min. Res. Hydrol. Rept. 4: 1-80. Thomas, G. J. 1963. Study of a population of sphaeriid clams in a temporary pond. Nautilus 77: 37-43.

ONO •=1,-- 1965. Growth in one species of sphaeriid clam. Nautilus 79: 47-54.

Trdan, R. J., and Hoeh, W. R. 1982. Eurytopic host use by two congeneric species of freshwater mussel (Pelecypoda: Union- idae: Anodonta). Amer. Midi. Nat. 108: 381-388. Tucker, M. E. 1927. Morphology of the glochidium and juvenile of the mussel Anodonta imbecillis. Trans. Amer. Micr. Soc. 46: 286-293. JD-31

Van Cleave, H. J., et al. 1947. Preliminary observations on reproduction in the molluscan genus Musculium. Nautilus 61: 6-11.

Van der Schalie, Henry. 1970. Hermaphroditism among North Amer- ican freshwater mussels. Malacologia 10: 93-112.

Way, C. M., et al. 1980. Comparative life history tactics of the sphaeriid clam, Musculium partumeium (Say), from a permanent and a temporary pond. Amer. Midi. Nat. 104: 319-327.