https://doi.org/10.24199/j.mmv.1978.39.03 7 July 1978

THE OMPHALOCIRRIDAE: A NEW FAMILY OF PALAEOZOIC GASTROPODA WHICH EXHIBITS SEXUAL DIMORPHISM By Robert M. Linsley

Department of Geology, Colgate University, Hamilton. New York, USA

Abstract

A careful study of the gastropod Hypomphalocirms rugosits (gen. et sp. nov.) from the Middle Devonian of Northeastern Michigan demonstrated that in this population two distinct morphotypes are present. Both morphotypes persisted throughout the entire sixty feet of the limestone and over fifty miles of lateral distribution. This suggests that they might possibly be male and female dimorphs. Tn order to check this as a possible explanation, re- lated species were studied from Germany, Manitoba and Australia. In all cases two morpho- types were present in an approximate one-to-one ratio, but only in Australia was a large enough sample present to be of significance (one hundred specimens from Australia, com- pared to a dozen specimens from Germany and Manitoba). This study has resulted in the erection of a new family (the Omphalocirridae), one new genus {Hypomphalocirms), one resurrected genus {Liomplwlus, Chapman) and one new species {Hypompltalocimts rugosus). The genus ArctamphaLus Toemachov, 1926, is sup- pressed as a synonym of Omphalocirrus. The discovery of multispiral opercula in place in three of the genera demonstrate conclusively that these snails are dextral rather than sinistral as has frequently been suggested. for The functional significance of the dimorphism is considered a mode of life established the organisms and the probable evolutionary sequence suggested.

in Sexual Dimorphism in Gastropoda difference by itself will be unrecognizable fossil populations. However if there are mor- Sexual dimorphism of shell shape, size and Phologic differences whtch allow one to sort radular form are all well-known phenomena the population into two samples, then pre- among living archaeogastropods and caenogas- tropods (Baker, 1926; Lamy, 1937; Robert- sumably a size distinction could be made. variety son, 1971; Sohl, 1969). Most commonly the In the case of the Omphalocirridae a allowed the difference takes the form of a larger average of criteria were discovered which population to be (or maximum) size for the female. Differences mature members of the ubiquitous in form generally are expressed in a greater divided into two subsets. The most present. All rate of expansion of the generating curve in distinction is the type of coiling characterized by the female which usually results in a relatively members of this family are can nor- lower spired trochoid shell (a 'fatter' shell), discoidal shells, but mature members orthostrophic or Both of these differences are generally thought mally be designated either as that may be used to be adaptive to accommodate the bulky eggs hypestrophic. Other features the degree produced by the female. Radular differences to differentiate the two subsets are collabral ornamentation, the may reflect food differences as in the case of of development of or spines, the the archaeogastropod Tricolia (Hiloa) variabil- degree of development of a keel the whorl profile, and the inclma- is (Pease) where the female feeds preferentially roundness of Sorting of the on brown alga (Padina) while the male lives on tion of the outer whorl face. above features, top of the female's shell preceding and during population on the basis of the makes it pos- the mating season, and presumably the radular either singly or in combination, these subsets also exhibit differences in the male allow it to feed on the sible to show that individuals in epiphytes on the female's shell (Robertson, a distinction of the size of the subsets. It is assumed in this paper that 1971, p. 77). tnese the Obviously radular differences will be of no the subsets of the population containing represent the females. help in sexing fossil gastropods. Similarly size largest individuals

33 34 ROBERT M. LINSLEY

Systematic Paleontology groups. In each of these groups this combina- only a single gill Class GASTROPODA Cuvier, 1797 tion of features suggest that exists (Knight, Batten and Yochelson, 1960, Subclass PROSOBRANCHIA Milne p. 1196) and supports the contention that this is Edwards, 1848 the case for the entire superfamily. Order ARCHAEOGASTROPODA The Omphalocirridae also resemble the gas- Thiele, 1925 tropods presently placed in superfamily Orio- Suborder MACLUR1TJNA Cox and stomatacea (Suborder Thochina, Knight, Bat- Knight, 1960 ten and Yochelson, 1960, p. 1245) in that both Superfamily EUOMPHALACEA dc Koninck, groups have radial apertures and multispiral, 1881 calcareous opercula. It is probable that the Oriostomatacca should be transferred to the Family Omphalocirridae new family Euomphalacea and, if it could be demon- Type genus Omphalocirrus, Ryckholt, 1860 strated that they exhibit sexual dimorphism, to the Omphalocirridae. Description: Large, dextral, discoidal gastro- pods varying from gently orthostrophic to Genus HYPOMPHALOCIRRUS gen nov. gently hypertrophic; whorl profile varying Type species: H, rugosus sp. nov. from subcircular to subtriangular, frequently Description: Large, dextral gastropods with with a marked circumbilical keel or spines spire very low to hyperstrophically depressed; on base; base broadly phaneromphalous; aper- whorl profile subtriangular with flattened up- ture subcircular. Early whorls filled with septa per, outer and lower faces joining at marked at maturity. Operculum disc-shaped, multi- angulations; base broadly phaneromphalous; spiral. All known members exhibiting varying the juncture between the outer whorl face and degrees of sexual dimorphism. the base typically developing canal-like projec- Discussion: The Omphalocirridae are readily tions which may also occur at juncture be- distinguished from the Helicotomidae and tween upper and outer whorl faces. Earlier Omphalotrochidae in being discoidal, while whorls filled with septa at maturity. Opercu- most members of the latter two families pos- lum disc-shaped, multispiral. Sexual dimor- sess elevated spires. The Omphalocirridae also phism strongly developed. differ from these two families in having an Discussion: The most abundant and obvious abundance of septa filling the early whorls. The fossil in the Rogers City Limestone is the Omphalocirridae resemble the Euomphalidae large euomphalid gastropod previously known in these two characters of septation and discoi- as Omphalocirrus manitohensis Whiteaves (Eh- dal form, but are distinguished from the Euom- Iers and Radabaugh, 1938; Ehlers and Kes- phalidae and all other Euomphalacea in hav- ling, 1970). Close study of about 200 speci- ing a calcareous, multispiral operculum and mens from the collections of the University of exhibiting sexual dimorphism. Michigan Museum of Paleontology, the U.S. As is true of all Euomphalacea the Ompha- National Museum and Colgate University show locirridae possess an aperture whose plane that this euomphalid not only is not conspeciiic passes through the axis of coiling Cradial aper- with Whiteaves species but that both the ture'), and some of the genera possess an an- Rogers City material and the material from gulation near the upper whorl face that is in- Manitoba are sufficiently distinct from Ompha- terpreted as exhalent. They resemble the Om- locirrus goldfttssi to warrant the establishment phalotrochidae in that some members of both of a new genus (also see Yochelson, 1966, p. groups possess a second angulation near the 41). base that resembles a siphonal canal or an in- This genus is most readily characterized by halent angulation. The uniqueness of the form the subtriangular whorl profile and the angular of these angulations suggests that they were meeting of the outer whorl face with the base developed independently in each of the two and upper whorl face. It is obviously closely OMPHALOCIRRIDAE 35 related to Omphalocimis but this latter genus ful stages, but varying in the adult from flat- has a rounded whorl profile. Both of these tened to a considerably depressed spire. Shell genera possess the unusual feature of canal- widely phaneromphalous with umbilical angle like projections at the juncture of the base and varying from 120° to 180°, depending on the outer whorl face. In addition it bears close degree of hyperstrophism. Growth lines on similarity to the Australian genus Liomphalus, upper whorl face generally opisthocline, begin- even though the latter lacks the canal-like pro- ning perpendicular to suture and culminating tuberances. at a 45° angle at the periphery; growth lines Two species are assigned to this genus. One prosocyrt on outer whorl face, continuing onto (H. rugosus) is herein described for the first base with backward obliquity and backward time, while the second is Whiteaves species H. concavity; normal course of growth line de- manitobensis (Whiteaves) from the Winni- flected both by undulations on shoulder and pegosis Limestone of Manitoba, Canada. In canal-like projections on the base. Ornament addition the specimen described from the An- consisting of strong collabral ornamentation derdon Limestone of the Michigan Basin (Lin- in youth, giving way to simple growth lines at sley, 1968) probably also belongs to this genus, maturity; in mature forms, interruptions in but it is too poorly known to describe formally. growth frequently resulting in rugose appear- ance; outer whorl face sometimes developing Hyomphalocimis rugosus sp. nov. roughened appearance in adult, (Plates 2-6) even develop- ing low canal-like projections. Shell very Herein designated type species. thick at junctures of the three whorl faces, thin Omphalocirrus manitobensis Ehlers and Rada- at centres of each whorl face, resulting in a baugh 1938 subcircular inner whorl profile and a subtri- Omphalocimis manitobensis Anonymous angular outer whorl profile. Septa abundant Omphalocirrus manitobensis Ehlers and Kes- and evenly spaced in the early whorls of ma- ling 1970 ture individuals. Operculum circular, disc- Description: Large, discoidal, dextral gastro- shaped multispiral, expanding counterclock- pods with sub-triangular whorl profile, with wise, all volutions visible on outer surface; angular base bearing canal-like projections or upper surface of each opercular volution in- a keel. Nuclear whorls smooth, simple, dextral. clined inward with slight rounding towards Whorl profile sub-triangular in shape with preceding whorl; outer face of opercular whorl outer whorl face varying from vertical (parallel parallel to axis of coil, resulting in deep, sharp to axis of coiling) to inclined outward at a suture separating each volution; early opercu- 45° angle. Upper whorl face varying from flat lar volutions (first ten or eleven) increasing in and horizontal to roundly dipping into spire; size logarithmically; later volutions (last five or outer whorl face flattened to broadly arched, ten) more irregular, approximately maintaining basal whorl face gently rounding into umbili- constant size and thus increasing in an archi- cus. Junction of upper and outer whorl faces median rather than logarithmic spiral; inner joining at an acute angle forming a smooth surface of operculum poorly known. keel or distinctly undulating keel. Junction of Holotype measuring 102-6 mm in width and outer and lower whorl faces typically sharp, 36-4 mm in height. Largest Paratype measur- occasionally rounded and bearing a series of ing 149 mm in width. canal-like projections or flanges which are Holotype—UMMP 22377; Figured Paratypes— sometimes replaced by a single or double keel UMMP 22375, 22378, 22379, 22380, 22383, 22384, in the adult. Upper suture varying from indis- 57888, 57889. USNM 102939, 213754, 213755 tinct to very sharp and deep with considerable 213756, 213757, 213758, 213759, 213760, 213761, overhang of ultimate whorl; umbilical suture 213762, 213763, 213764, 213765, 213766, 213767, 213768, 213769, 213770, 213772, sharp and deeply incised, occurring just out- 213773, 213774, 213775, 213776, 213777, 213778, 213779, 213780, side of the umbilical ridge of the preceding 213781, 213782, 213783. Unfigured Paratopes— whorl. Upper shell surface flattened in youth- UMMP 22381, 22382, 22385. USNM 213771. 36 ROBERT M. LINSLEY

Discussion: Hypompiialocirrus rugosis is a very whorl, to UMMP 213758 (pi. 4, fig. 7) where large gastropod (150 mm) that rivals the size the upper surface of the ultimate whorl strikes of the largest Macluritida. Among Paleozoic the ultimate whorl two-thirds the way down Gastropoda only Straparollus grandis (Ko- the ultimate whorl. The geometry of the whorl

ninck 1 ( 30 mm ) Pithodea amplissa, Ko- profile is such that variation in the amount of ninck (140 mm) from the carboniferous of hyperstrophism also is associated with other Belgium, Arctomphalus grandis Tolmachotf changes in the whorl profile. As the degree of (now Omphalocirrus goldfussi) (170 mm) and hyperstrophism increases the entire triangular a Carboniferous euomphalid (210 mm) re- whorl profile of the shell rotates so that the ported by Yochelson (1966) as being in the outer whorl face varies from being inclined British Geological Survey and Museum can almost 45° to the axis of coiling in the male compare in size with this new species. (see USNM 213775, pi. 2, fig. 4) to almost The diagnostic features of this species are parallel to the axis of coiling in the female the sub-triangular whorl profile, the tendency (see UMMP 22377, pi. 4, fig. 2). The round- to develop flanges at the upper angulation of ness of the upper whorl face also seems to in- the female, and canal-like projections on the crease with increased hyperstrophism (UMMP base. However there is considerable variation 22377 and USNM 213758, pi. 4, figs. 6, 7) of each of these features within the population and of course umbilical depth decreases as hy- of about two hundred individuals that were perstrophism increases. UMMP 22377 (pi. 4, studied. figs. 5, 6) has an umbilical angle of 180° while Females of H. nigosus can be distinguished USNM 213759 (pi. 6, fig. 3) has an umbilical from females of H. manitobensis (Whiteaves) angle of about 150° and USNM 213758 (pi. by the presence of a second row of canal-like 4, fig. 7) is so depressed that one could talk projections which the latter bears on the upper about an 'umbilical spire'. angulation. The whorl profile of H. manito- Other features, equally variable, do not bensis has the triangular profile tilted so that seem to be related to the degree of hyper- the outer whorl face is subparallel to the axis strophism. The proportionate size of the of coiling and the periphery of the shell is at outer whorl face may be rather small (UMMP the midpoint of the rounded whorl face rather 22379, pi. 6, fig. 8) or very great USNM than at the upper angulation as it is in H. rugo- 213759 (pi. 6, fig. 3). Some features are ob- sus. H. manitobensis has assumed an almost viously related to age. Immature forms of isotrophic coiling and thus appears to converge males are very difficult and sometimes impos- on a bellerophont-like form. sible to distinguish from those of females. Im- The single, poorly preserved specimen of mature forms tend to have well-developed col- Hypompiialocirrus described from the Ander- labral ornamentation (UMMP 22375, pi. 5, don Limestone (Linsley, 1968) is not well fig. 7, early whorls of USNM 213760, pi. 5,' enough known to warrant a formal description. fig. 3). Immature specimens (UMMP 22375, The chief distinction is the bundling of growth pi. 5, fig. 7) also tend to have a smooth junc- lines found in this species. Five or six growth ture between the upper and outer whorl faces. lines are subparallel to each other and all Rarely this feature will be carried into maturity participate in making up a single basal projec- in the females (UMMP 57888, pi. 5, fig. 4 and tion. The next set of prominent growth lines USNM 213781, pi. 6, fig. 5). More fre- then diverge sharply from the preceding set to quently this upper juncture develops into a form the next basal projection. scalloped flange at maturity, either with a Within the population of females of H. gentle fluting (UMMP 22379, pi. 5, fig. 6 and rugosus the degree of hyperstrophism is still pi. 6, fig. 1) or in a few cases very pronounced, highly variable ranging from USNM 213781 almost grotesque fluting (USNM 213772, pi. 6, (pi. 6, fig. 5) where the upper surface of the fig. 4 and USNM 213754, pi. 6, figs. 10, 11). penultimate whorl strikes the ultimate whorl In the holotype (UMMP 22377, pi. 4, fig. 6) about one-third the way down the ultimate the ultimate whorl is well fluted until the last OMPHALOCIRRIDAE 37 i volution, when the fluting ceases. There maintaining an essentially flat upper surface. seems to be some tendency for the degree of The outer whorl face occasionally shows a fluting to be related to the amount of sculpture faint, revolving ornamental groove just below present on the outer whorl face. In general the the periphery (USNM 213779, pi. 3, fig. 4, greater the fluting, the more sculpture. The USNM 213773, pi. 3, fig. 6 and USNM sculpture varies tremendously from raised 213778, pi. 3, fig. 9). The outer whorl face is growth lines (USNM 213754, pi. 6, fig. 11) to generally flattened, but a few individuals, es- small ridges perpendicular to the growth lines pecially USNM 213761 (pi. 3, fig. 12) and (USNM 213759, pi. 6, fig. 3) large bumps USNM 213756 (pi. 3, fig. 13) exhibit a very (USNM 213765, pi. 6, fig. 7) or even canal- rounded whorl profile. The most marked varia- like foldings of the growth lines (USNM tion in the males occurs on the base relative to 213772, pi. 6, fig. 4). the circumbilical ridge. The ridge develops The canal-like projections on the basal an- very early at the end of the second volution. gulation are a most persistent feature of the During this early stage canal-like projections females. Their position on the base is depen- develop very much like those of the females. dent upon the amount of hyperstrophism and However in the males the projections rarely the subsequent rotation of subtriangular whorl persist beyond the third whorl. An exception is profile. Where hyperstrophism is not great and USNM 213773 (pi. 3, fig. 6) which maintains outward rotation of the outer whorl face mini- very large, fully developed spines through ma- mal, the projections will appear to be in the turity. In most mature individuals (USNM middle of the whorl as seen from the base 213775, pi. 3, fig. 8 and USNM 213766, pi. (UMMP 22378, pi. 6; fig. 2 and USNM 3, fig. 5) the mature whorls have only a rela- 213760, pi. 5, fig. 3). When hyperstrophism is tively sharp ridge, perhaps with only faint strongly developed and outward rotation of suggestions of protrusions (USNM 102939, the outer whorl face is substantial (UMMP pi. 3, figs. 1, 11). In at least one example 22377, pi. 4, fig. 5) the projections will appear (USNM 213757, pi. 3, fig. 3) a double ridge to be at the periphery of the whorl as seen results. In one other case (USNM 213756, pi. from the base. The shape of these projections 3, fig. 13) there is no sign of a keel at all, but varies from the typical rather slender ones rather the base is very rounded and the growth (UMMP 22377, pi. 4, figs. 5, 8 and USNM lines are unusually rugose at maturity. 213764, pi. 5, fig. 2) to very broad, spade-like Dr G. Arthur Cooper of the U.S. National projections (USNM 213767, pi. 5, fig. 5). Museum kindly brought to my attention a One specimen, UMMP 22380 (pi. 6, fig. 9) collection of gastropods from the Miami Bend is the most aberrant of the collection. It has a Formation of Indiana (Cooper and Phelan, very swollen, rounded whorl profile and thus 1966). Most of the collection consists of stein- seems to closely resemble Omphalocirrus kerns which are generically and specifically goldfussi. In all other respects, such as the indeterminate, but a few molds were collected sculptured, outwardly rotated outer whorl face, which can be identified. One of these (USNM

etc. it resembles H. rugosus and I have thus 213769, pi. 2, fig. 6) is a partially complete im- treated merely as one aberrant member of a pression of the spire of a male Hypomphalo- very diverse population. cirrus rugosus. This adds one more small piece The males of Hypomphalocirrus rugosus of evidence to their mass of data supporting may be readily distinguished from the fe- their claim for a correlation of the Miami males by their flat upper whorl face and by Bend Formation with the Rogers City Lime- the fact that the spire is flush, with the upper stone. whorl faces continuous with each other rather The wide latitude of variation present in this than the depressed spire so typical in the fe- species is in part explained by the morpholo- males. gical differences between the males and fe- The males exhibit less variation than the males. The existence of these two subsets of females. The spire profile is very constant, this population can best be seen in the graph 38 ROBERT M. LINSLEY

per- in Fig. 1 , which plots size against a measure of isthocline on upper whorl face, beginning the degree of hyperstrophism (umbilical width pendicular to suture and proceeding with a divided by umbilical depth). This plot demon- forward obliquity and marked backward con- strates that though the youthful individuals are cavity; at periphery growth lines variable de- inseparable, the adults separate into two dis- pending on the position relative to flange; pre- tinct populations. This is, of course, perfectly sence of flange causing growth line to bend consistent with an interpretation of sexual di- backward from its opisthocline course, mak- morphism. ing it subparallel to suture once again; growth Using the degree of hyperstrophism as a lines continuing on outer whorl face in proso- criterion for establishing two populations, cyrt fashion; at junction of outer whorl face many other distinctions were discovered and base, growth lines interfered with by which correlate with this character. The follow- canal-like projections; growth lines bending ing paragraphs are formalized descriptions of back rather strongly in a U-shape to partici- the females and males. pate in formation of spine, bending forward Description of females: Large, shallowly hy- in an V shape in front of completed spine, pertrophic gastropods with well-developed continuing uninterruptedly where no spine is canal-like projections at the junction of the present. Ornament consisting of collabral orna- outer whorl face with the base. Nucleus smooth, ment in youth, giving way to growth lines in simple and dextral. Whorl profile subtriangu- adult; growth lines becoming crowded during lar in shape, outer whorl face tilted in slightly spine formation causing adult to have rugose from perpendicular. Upper whorl face flattened appearance; flanges or undulations developing near periphery, gradually curving downward along periphery in adult; canal-like projections near preceding whorls and curving downward around base tending to become very strong in abruptly at suture, so that inner edge of upper adult; outer whorl face tending to become whorl face overhangs upper whorl face of roughened in adult, developing low, rugose, preceding whorl; upper whorl face adjoining and in extreme cases, even canal-like projec- outer whorl face at periphery with a marked tions. Shell thickness exceedingly variable, be- keel; keel smooth in youthful stages, but at ing thin at centre of each whorl face and be- maturity keel tending to develop pronounced coming very thick at junctures of whorl faces, periodic undulations; outer whorl face gently resulting in a subtriangular outer whorl pro- rounded, sloping inward and downward from file and subcircular to elliptical inner whorl peripherally located junction with upper whorl profile. Septa abundant in earlier whorls in face; outer whorl face adjoining base forming mature shells, unevenly spaced at about eight a keel which develops canal-like projections at to twelve per whorl. a very early stage; canal-like projections gene- Holotype measuring 102-6 mm in width and rally becoming larger and better developed with 36-4 mm in height. Largest paratype measur- maturity; basal whorl face flattened, proceed- ing 149 mm in width. ing upward towards umbilical suture from its Holotvpe—XJMMP 22377; Figured Paratvpes— junction with outer whorl face. Upper suture UMMP 22375, 22378, 22379, 22380, 22383. USNM fairly deep, sharply incised with ultimate whorl 213760, 213764, 213758, 213754, 213765, 213772, slightly overhanging penultimate whorl; um- 213776, 213755, 213768, 213767. Unfigured Para- types—UMMP 2238 J, 22382, 22385. bilical suture sharp and very deep, occurring outside of the canal-like projections of pre- Description of males: Large, flat-topped ortho- ceding whorl. Early whorls depressed below strophic gastropods with a subtriangular whorl mature whorls resulting in hyperstrophic whorl profile and sharp angular base bearing either a profile. Degree of hyperstrophism quite vari- keel or canal-like projections. Nuclear whorls able, but generally increasing with maturity. smooth, simple, dextral. Whorl profile re- Shell widely phaneromphalous, with umbilical sembling an equilateral triangle with upper angle varying from 150°to 180° depending whorl face horizontal or perpendicular to axis on degree of hyperstrophism. Growth lines op- of coiling. Upper whorl face flat, bending OMPHALOCIRRIDAE 39 downward very slightly at the surface. Outer generate into a keel while in the female these whorl face joining upper whorl face at a sharp projections become larger in the adults, pre- angle at shell periphery, forming a sharp sumably remaining functional throughout its smooth keel. Outer whorl profile flattened to life. Assuming that these do indeed facilitate in- gently rounded; typically with slight concavities current water, this would again be consistent just below peripheral keel and just above ba- with the increased oxygen needs of the female sal keel, occasionally gently rounded from in producing the bulky egg masses. In addition keel to keel. Basal whorl face joining outer the increased hypcrstrophicity of the female whorl at sharp angulation and progressing would appear to be due to, or at least accom- flatly or with gently rounding to umbilical su- panied by, the rotation of the whorl profile. ture. Upper suture varying from indistinct This rotation brings the outer whorl face into to sharp with slight overhang of inner whorl a sub-vertical position (parallel to the axis edge over preceding whorl; umbilical suture of coiling) thus bringing both incurrent and sharp, frequently deep, normally just outside excurrent openings into a peripheral position circumbilical ridge. Upper shell surface flat- which would again facilitate water movement tened, not depressed. Base widely and deeply through the mantle. The male, with less critical phaneromphalous; umbilical angle varying be- circulatory demands tends to keep the in- tween 120° 145°. to Growth lines on upper current opening at a slightly less favourable whorl face beginning perpendicular to the su- position in order to better position the anus ture and proceeding opisthoclinally towards at the extreme periphery. The male also tends the periphery, intersecting periphery at 45° to loose the incurrent canals, which were ap- angle; growth lines prosocyrt on outer whorl parently useful during the rapid growth of face, continuing with strong collabral orna- youth, but no longer so crucial to success in mentation, normally reducing to faint growth the adult. lines in adult; strong angular keel at periphery It is possible that the collabral ornamenta- at junction of upper and outer whorl faces; tion of the immature shells served to strengthen faint revolving groove sometimes developed on those shells. As the shell increased in size it outer whorl face, just below periphery. Cir- also increases in thickness, apparently to the cumbilical ridge developing early with well- point where the collabral ornamentation lost developed canal-like projections; in maturity, its functional significance and so disappears circumbilical ridge normally reverting to single on the adults. or double ridge, rarely retaining canal-like pro- Hypomphalocirms manitobensis (Whiteaves) jections to maturity. Shell thick, particularly at Euomphalus manitobensis Whiteaves keels, resulting in subtriangular outer whorl 1890, p. 100, pi. 6, figs. 2-26. profile and subcircular to elliptical inner whorl profile. Septa present through much of early Omphalocirrus manitobensis Whiteaves 1892, portion of mature shell. Shell width of largest p. 327, pi. 43, figs. 5-7. paratype 110 mm. (Plate 7, figures 1-8) Androtvpe—USNM 102939; Paratypes—UMMP 22382, 22384. USNM 213775, 213770, 213762, Description: Large, slightly hyperstrophic gas- 213763, 213777, 213757, 213778, 213779, 213773, tropods with one or two rows of canal-like 213766, 213774, 213769, 213761, 213756, 213780. extensions at boundaries of outer whorl face. Unfigured Paratype—213771. Nucleus poorly known, apparently smooth and Discussion continued; Briefly, the main fea- dextral. Whorl profile varying from subtri- tures of each sex can be summed as follows. angular in the females, to suboval in shape in The females tend to be larger than the males, the males. In females the upper whorl face a feature similar to so many modern gastro- meeting outer whorl face to form a keel pods and presumably related to the greater which may bear long canal-like projections, bulk of eggs of the female. The canal-like pro- then proceeds roundly down to suture; outer jections on the base of the males usually de- whorl face of females broadly rounded 40 ROBERT M. LINSLEY and meeting lower whorl face at a keel which above description is based on material from the also may bear canal-like protuberances similar Winnepegosan Limestone as our knowledge of to those on top; basal whorl face continuing Hypomphalocirrus manitohensis at this time roundly up to the umbilical suture to complete is based entirely on those specimens. the rounded equilateral triangle. Whorl profile The collection available for study of this of males more rounded with less distinct keels, species consists of fifteen specimens collected bearing canal-like projections only on base. by Linsley and Cottrell in 1968 from locality Upper suture deep, sharply incised. Umbilical 1 8 of the Field Guide to Devonian Outcrops of suture distinct, deeper in females than in males. Southwestern Manitoba (McCabe, 1967). This Aperture, as determined from observations of locality is about one mile west of the Narrows, growth lines, gently opisthocline on upper on Lake Winnepegosis. In addition, Whiteaves whorl face, bending back at periphery to form types (GSC 4174, 4176, 4177) from the Geo- upper rows of canal-like projections, continu- logical Survey of Canada at Ottawa were ing on outer whorl face in prosocyrt fashion kindly made available for study. While seven- and on to the base with a gently backward con- teen specimens do not constitute a large enough cavity, again involved with canal formation at collection on which one might base a definitive the juncture of the base with the outer whorl study, they do suggest that two distinct mor- face. Males with greater hypcrstrophism than photypes are present and may best be regarded females; base of males being relatively flat as males and females. while females deviating only slightly from dis- The females (pi. 7, figs. 3, 5, 6, 8) are coidal. Ornament consisting of strong collabral characterized by a triangular whorl profile and ornament in males with one row of canal-like have well-developed canal-like protrusions at projections on the base; ornament in females both boundaries of the outer whorl face. As consisting only of fine growth lines with two this form is regarded as having evolved from rows of canal-like projections both above //. rug&sus, it would seem a natural develop- and below the outer whorl face. Outer whorl ment for the undulating shoulder of the Rogers face sometimes roughened in adult females. City females to have developed into the true Shell moderately thick, particularly at junc- canals of the Manitoba form, thus perfecting tions of whorl faces. Septa fairly abundant in the current flow in and out of the mantle cavity. mature individuals. Operculum thin, and disc- The females of H. manitohensis also resemble shaped, circular in outline, multispiral, ex- the females of H. rugosus in having a sub- panding counterclockwise with all volutions vertical outer whorl face, a fair degree of hy- visible on outer surface. perstrophicity, and rugosities on the outer Lectotype—GSC 4173; Picsiotypes—GSC 4163a, whorl face. 4174, 4175, 4176, 4177; Ifvpotvpes—USNM 213782, The males of the Winnepegosis Formation 213783. differ markedly from the Rogers City forms. Discussion: Yochelson (1966, p. 41) has al- The males of //. manitohensis are more hyper- ready treated the problems attendant on this strophic than the females which suggests that species. Whiteaves (1890, p. 100) original the degree of hyperstrophism is important only specimens of H. manitohensis are steinkerns as it affects the position of the incurrent or ex- from the Dawson Bay Limestone. These current water streams. The basal canal-like ex- are generically indeterminate. Subsequently, tensions on the males of H. manitohensis are Whiteaves (1892, p. 327, pi. 43, figs. 5-7) re- positioned only slightly more peripherally than described this species and reassigned it to the their H. rugosus counterparts. The rest of the genus Omphalocirms, but this was done prim- whorl profile of the H. manitohensis males is arily on the basis of material obtained from much more rounded than either the females or the Winnipegosan Limestone which underlies the Rogers City forms. However they resemble the Dawson Bay Limestone. There is no cer- the males of the Rogers City forms by having tain way of knowing whether or not the speci- much stronger collabral ornament than that mens from these two units are conspecific. The possessed by the females. OMPHALOCIRRIDAE 41

Omphalocirrus goldfussi (Archiac and ascertain whether or not the dimorphism ap- parent Verneuil)—(Plate 8) in the half-dozen specimens at my dis- posal holds true for the entire population. Knight (1941, pp. 45, 213) and Yochelson Genus (1966, p. 42) have both offered excellent des- Liomphalus Chapman, 1916, p. 90 criptions and synonymies of Omphalocirrus Type species: Liomphalus australis by original goldfussi; (Archiac and Verneuil, 1842) and designation Arctomphalus grandis Tolmachoff, 1926. I am Description: Large, discoidal, septate gastro- familiar with this genus only through their pods with low to hyperstrophically depressed works and through a careful study of the spire. Outer whorl profile varying from sub- plastotype material made available to me from circular to subtriangular with circular inner the National US Museum. This study has led whorl profile. Strong circumbilical ridge with me to the conclusion that 'Arctomphalus gran- no canal-like projections. Operculum disc- dis' is the sexual dimorph (probably male) of shaped, multispiral. Sexual dimorphism Omphalocirrus goldfussi. Plate 8, fig. 7 is an weakly developed. illustration of the lectotype of Arctomphalus Discussion: Like the other members of the grandis (Specimen A-19229, Paleontologisk family Omphalocirridae, this genus exhibits Museum of Oslo). Unfortunately the outer sexual dimorphism. However compared to the volution, represented by the broken line in the other genera, the sexual dimorphism of Liom- figure, is a steinkern and only an impression of phalus seems poorly developed, as though it the basal suture of the inner whorls remains. were an incipient feature. This feature is con- However comparison of this remnant with sistent with its lower stratigraphic position and some German material of Omphalocirrus gold- presumed ancestry to the other members of fussi (see pi. 8, figs. 4, 5, 9) illustrates that all the family. Liomphalus also resembles the other of these specimens are similar in that they are members of this family by being septate, dis- hyperstrophic, have strong collabral ornament coidal gastropods which bear a disc-shaped, and have a circumbilical ridge which develops multispiral calcareous operculum (see also periodic nodes which are only occasionally de- Yochelson and Linsley, 1972). It can readily veloped into canal-like projections. Collec- be differentiated from other members of this tively, these features suggest male characters family by the presence of a circumbilical of Hypomphalocirrus rugosus and H. manito- ridge without any suggestion of nodes or canal- bensis. The other types of Omphalocirrus gold- like extensions on it. fussi (PL 8, figs. 1-3, 6, 8) are quite distinct from those described above. They are all or- Liomphalus northi (Etheridge) 1890 thostrophic, have much weaker collabral orna- Plate 9, 10 mentation and have well-developed, apparently 1890 Oriostoma northi Etheridge, p. 64, pi. 9, figs. 6-7 functional canal-like extensions which appear 1894 Oriostoma northi Etheridge, p. 151, pi. 9, fiss. in early youth and persist through maturity. 1-4 1894 Euomphalus (Oriostoma) northi In addition this morphotype has a very pro- Etheridge; Cresswell, p. 157 nounced swollen form due to a greater rate of 1913 Euomphalus northi (Etheridge); Chapman, p. expansion of the generating curve. All of 227 these features are consistent with the interpre- 1916 Euomphalus northi (Etheridge); Chapman, p. 90 tation of this form as the female. 1916 Liomphalus australis Chapman, p. 90, pi. 4, figs. 32-33 To date no opercula have been found asso- 1959 Straparollus (Euomphalus) northi (Etheridge); goldfussi, but I fully expect ciated with O. Philip and Talent p. 50, pi. 7, figs. 1-21, pi. 8, multispiralled opercula to occur in the same figs. 1-2 Oriostoma beds and with great fortune to be found in a 1972 northi Etheridge; Yochelson and Lin- sley, p. 8, pi. 1, fig. 6, pi. 2, figs. 1-5 life situation, well back from the aperture. It 1976 Straparollus (Euomphalus) northi Etheridge; would also be beneficial if a study could be Tassell, p. 9, pi. 1, figs. 7, 8, pi. 2, fig. 11, pi. 3, made on a large population of this species to figs. 1,2,7,8 42 ROBERT M. LINSLEY

Description: Shells large, discoidal, varying width of largest hypotype measuring 98 mm. from flatly orthostrophic to slightly hypertro- Figured Hvpotypes—NMV PI 107, P28373, P28498, phic with distinct circumbilical ridge. Nuclear P28499, P28707, P28708, P287Q9, P28710, P287I1, whorls unknown, presumably simple, smooth P28712, P28713, P28714, P287I5, P287J6, P28717, P287l8and P28719. and dextral. Whorl profile subrectangular in youthful stages, changing to subelliptical or Description of males: Shell large, discoidal, subtriangular in adults. Upper whorl face vari- slightly hyperstrophic. Nucleus unknown, pre- able, ranging from broadly arched and con- sumably normal dextral. Whorl profile varying fluent with upper whorl face, to gently arched from subelliptical to distinctly subtriangular, and meeting outer whorl face of a distinct keel; typically with marked bilateral symmetry con- marked keel separating upper and outer whorl verging to isostrophism. Upper whorl face faces typically present in immature forms, but typically gently arched to the keel-like shoul- disappearing in many members of the adult der separating upper and outer whorl faces; population; outer whorl face strongly rounded, keel-like shoulder occasionally absent with joined lower whorl face at pronounced circum- upper and outer whorl faces roundly confluent bilical ridge; lower whorl face with slight con- with one another. Outer whorl face rather cavity inside circumbilical ridge, continuing strongly convex between upper keel-like flatly to umbilical suture. Both upper and um- shoulder and circumbilical ridge; lower whorl bilical sutures shallow but distinct; depth of face flattened to umbilical shoulder. Upper sutures varying with degree of spire depression suture distinct but not sharply incised; um- with deeper suture generally present on flattest bilical suture slightly deeper, also sharply in- surface. Shells varying from slightly ortho- cised. Shell basically hyperstrophic but vari- strophic to slightly hypertrophic, sometimes able in degree. Growth lines orthocline on up- bordering on isostrophic, particularly in imma- per whorl face, opisthocyrt on outer whorl face ture shells. Growth lines orthocline on upper and slightly prosocline on lower whorl face whorl face, opisthocyrt on outer whorl face with gently prosocyrt areas over each keel. and slightly prosocline on lower whorl face, Ornament normally consisting of strong colla- opisthocyrt on outer whorl face and slightly bral ornament and two keels. Normally with prosocline on lower whorl face with gently strong collabral ornament on upper and lower prosocyrt bendings over keels when present. whorl faces with weaker collabral ornament Ornament of youthful forms consisting of occasionally absent on upper and outer whorl strong collabral lines and two keels above and faces. Normally with keel-like shoulder below the outer whorl face; in adult forms the separating upper from outer whorl faces and basal collabral ornamentation and keel invari- with circumbilical ridge separating outer and ably persist, but the upper collabral ornamen- basal whorl faces; upper ridge occasionally ab- tation gives way to fine, closely spaced growth sent. Septa common in early whorls, more rare lines in one-half the population; the keel sep- in mature whorls, but present to within one- arating the upper and outer whorl face fre- half volution of aperture. Operculum as in quently disappearing in one-half the adult orthostrophic individuals. Shell width of population. Shell thinnest near parietal lip, largest hypotype measuring 70 mm. sometimes present only as a parietal inductura; Ifypotvpes—NMV PJJ07, P28707 t P28710, shell becoming thicker near outer lip and P28713, P28714, P28715, P28717, P28718} P28719 t reaching maximum thickness (6 or 7 mm) at P28708. circumbilical ridge. Septa abundant in early Description of females: Shell large, discoidal portion of whorls of adult shells, becoming with depressed spire. Nucleus unknown. more widely and unevenly spaced in more Whorl profile subelliptical with long axis of mature whorls; may occasionally be placed ellipse perpendicular to axis of coiling, upper within one-half whorls distance from the aper- whorl face broadly rounded, usually continuing ture. Opiculum thick, circular, disc-shaped, without interruption to outer whorl face; outer multispiral, expanding counterclockwise. Shell whorl face more sharply rounded. Joining OMPHALOCIRRIDAE 43 lower whorl face at marked circumbilical keel; either Oriostoma or Straparollus 1 have utilized lower whorl face with slight concavity inside the genus Liomphalus. circumbilical ridge, then flattened before This species can be easily differentiated from rounding into umbilical suture. Upper suture other members of the Omphalocirridae by the shallow but distinct; umbilical suture more fact that its base lacks any nodal swellings or shallow but also distinct. Shells basically or- canal-like extensions. In addition, the sexual thostrophic tending towards planispiral, apical dimorphism while present, is not as well de- angle varying from 200° to 230°. Umbilical veloped as in the descendant, more advanced angle varying from about 130° to 160°. members of the family. The adult males of L. Growth lines closely spaced and very fine on northi tend to preserve juvenile features such upper whorl face, generally orthocline becom- as collabral ornamentation on the upper whorl ing very slightly opisthocline on outer whorl face in addition to a strong keel separating the face and very slightly prosocline on base re- upper and outer whorl faces. In addition the sulting in a slight prosocyrt phase over cir- males develop only a modest degree of hyper- cumbilical ridge. Growth lines becoming strophism. The upper surface of the females strong collabral ornamentation as they cross however lose both the keel and the collabral circumbilical ridge onto base. Ornamentation ornament so that their upper whorl face flows consisting of growth lines on upper and outer continuously into the outer whorl face and whorl faces, collabral ornamentation on base, has only closely-spaced, fine growth lines on with circumbilical ridge invariably present and it. The females also tend to be slightly ortho- shoulder separating upper and outer whorl strophic. However none of these sets of faces only rarely present. Shell thinnest near characters are inviolate. In the collection of parietal lip, sometimes present only as parie- 104 specimens available of the National Mu- tal inductura, occasionally with some degree of seum of Victoria, Melbourne, there were oc-

thickness to it. Shell becoming thicker (up to casional hypcrstrophic forms with a rounded four or five mm) near outer lip and reaching upper whorl face (PI. 10, fig. 12, NMV maximum thickness at circumbilical ridge. P28713) or a faint keel which faded out (PI. Septa numerous through early portion of 10, figs. 9, 10), but the great majority of the shell, becoming more widely spaced in mature members of this large population could be region, but occasionally present to within one- separated with ease^ half whorl of the aperture. Operculum thick, However, this incipient sexual dimorphism, circular, disc-shaped, multispiral, expanding the lack of canal-like projections and the low counterclockwise (for more complete descrip- stratigraphic position of L. northi are all con- tion, see Yochelson and Linsley, 1972). Shell sistent with the interpretation that this form is width of largest hypotype measuring 98 mm. ancestral to Omphalocirrus and Hypomphalo- cirrus. Hypotypes—NMV P28498, P28499, P28373, P28709, P28711, P28712 and P28716. Stratigraphic Distribution The oldest member of the family Omphalo- Discussion: Chapman based the genus Liom- cirridae is Liomphalus northi of the Lilydale phalus on some very poorly preserved speci- Limestone, Lower Devonian Yeringian of mens from the Lilydale Limestone which are Australia. It is considered to be late Siegenian undoubtedly abraded specimens of Etheridge's byStrusz(1972). species 'Oriostoma northi'. As a result his Although the next known occurrence of a original species of Liomphalus australis name member of this family is delayed until the

Chapman is invalid and should be Liomphalus Anderdon Limestone of the Michigan Basin, it northi (Etheridge). However, the generic name is probable that further examination of gastro- 'Liomphalus' is still a valid and available name, pods presently assigned to the family Euom- and since the new evidence presented in this phalidae will uncover other genera and species paper supports the removal of this species from that should be transferred to this group. The 44 ROBERT M. LINSLEY

Andcrdon form (Linsley, 1968) of Hypom- City-Miami Bend Formations are very slightly phalocirrus is unfortunately known only from older than the Winnipegosis Formation. a single fragment of an immature specimen. The last known occurrences of members of The Anderdon find represents the first known this family are those of Omphalocirrus gold- occurrence of this family in North America. fussi from the Givetian Stringocephalus beds The Anderdon represents a limited facics on of Europe and the lone occurrence of the same the southeastern flank of the Michigan basin species (ex-Arctomphalus grandis) from Goose and is thought to be Eifelian (see Fagerstrom, Fiord, Ellesmere Land, from the Blue Fiord

1961, and Linsley, 1968). It is considered to Formation of Eifelian age (McLaren, 1963, be late Sieyenian by Strusz (1972). pp. 324-328).

The next occurrence of a member of this General Considerations family is Hypomphalocirrus rugosus from the Rogers City Limestone of the North East cor- The genus Omphalocirrus, to which Hypom- ner of the Michigan Basin. This unit has been phalocirrus is closely related, has had a check- placed in the lowermost Givetian (Cooper and ered career in the literature, with no one being Phelan, 1966, Ehlers and Kesling, 1970, Lins- quite certain whether to place the canal-like ley 1973). Although this unit does not contain protrusions on the 'top' or on the 'bottom'. the brachiopod Sfringocephalus, it does contain Even within the past thirty years the beast has other members of the Stringocephalus fauna flipped three times. Knight 1 94 been ( 1 , p. such as Atrypa arctica, Subrensselandia n. sp., 213) considered the canal-like projections to Liromytilus attenuatus, Buechelia tyrellii, Car- be the base of the organism, but without much inatina dysmorphostrota (Ehlers and Kesling, conviction for he was not at all certain 'that 1970, p. 29) and Straparollus (Straparollus) the orientation employed . . . should not be cottrelli and S, (Eitomphalm) (Lins- hofjmani reversed' (Knight, 1941, p. 213). In 1952 (p. ley and Yochelson, 1973). 37) he reversed it, indicating that he con- The other occurrence of Hypomphalocirrus sidered Omphalocirrus to be a sinistrally coiled rugosus in the Miami Bend Formation of In- Macluritacean, and that the canal-like projec- diana adds to the already substantial array of tions served an exhalent function. This view evidence put forth by Cooper and Phelan was retained in the Treatise (Knight, Batten (1966) that this unit is directly correlative and Yochelson, 1960, p. 1189). In 1966, E. L. with the Rogers City Limestone. Yochelson (1966, p. 43, 45) broke from the Treatise triumvirate The Winnipegosis Formation of Manitoba and flipped Omphalocirrus once again, placing the is also generally considered to be of Lower projections on the base, assuming them to be purely Givetian age (Ehlers and Kesling, 1970, p. 29, ornamental with no function, and transferring Cooper and Phelan, 1966, p. 28, Baillie, 1951, the genus from the Macluritacea to the p. 59) and is generally correlated by these Euomphalacea. authors as the equivalent of the Rogers City In Whiteaves original description of H, Limestone. However a study of the species of manitohensis (Whiteaves, 1890, p. 100) he de- Hypomphalocirrus present in these two for- scribed a steinkern assigned to that species

mations suggests that the Rogers City form is that had an operculum associated with it. ancestral to the Winnipegosis form and thus Considerable doubt has always surrounded this must slightly antedate the latter. This view is association. The operculum in this fossil is also supported by the study of the middle positioned well back into the shell, away from Devonian carrier shell, Straparollus (Linsley the aperture and tilted at an angle that would and Yochelson, 1973) which suggests that the be unusual for an intact operculum (pi. 7, Rogers City species are ancestral to the Winni- fig. 2). It was impossible to demonstrate that pegosis species. Most certainly the two forma- this was not just an operculum that had floated tions are close in age to each other, but the into an empty shell. Added to this is the fact evidence on hand suggests that the Rogers that Whiteaves original description of H. mani- OMPHALOCIRRIDAE 45 tobensis (Whiteaves, 1890) was based on stein- tions of the shell (inhalent, exhalent, etc.). But kerns from the Dawson Bay Formation that the orientation of the shell during life remains are generically indeterminate and our present as much of an enigma as ever. understanding of the species is based on ma- In the majority of modern gastropods, i.e. terial collected from the underlying Winne- those with either high spires or elongated aper- pegosis Formation and assigned by Whiteaves tures (cones, mitres, volutes, terebras, etc.) the to H. manitobensis. To further complicate 'base' of the shell is actually the leading edge matters no opercula of a multispiral form were or anterior-most portion of the shell relative known either from the Euomphalacea or the to the living animal. In low-spired modern Macluritacea, and the operculum ascribed by gastropods (turbonids, naticids, trochids, etc.)

Whiteaves to t manitobensis did H not fit our or discoidal shells (planorbids, etc.) the 'outer understanding of either of these groups. lip' forms the leading edge of the shell. Thus in I have been fortunate enough to find oper- this second group the 'base' of the shell is the cula in place both in H. manitobensis (pi. 7, fig. left side and the spire projects back and to the 1) from the Winnipegosis Formation of Mani- right side of the animal. In all of these gastro- toba and in H. rugosus from the Rogers City pods the shell is held dorsally over the body by Limestone of Michigan. In both instances the the columellar muscle and the plane of the operculum is multispiral, set well back away aperture is parallel to the substrate. from the aperture and slightly tilted to the If the Omphalocirridae are 'typical' gastro- axis of the cone of revolution of the whorl, al- pods then the shell would be held in a dorsal though not as tilted as in Whiteaves specimen. position with the coiled portion resting on the Thus there can now be no doubt that Hypom- operculum of the upper surface of the pos- phalocirrus does indeed possess a multispiral terior portion of the foot (the metapodium). operculum. The discovery also lends credence However the Omphalocirridae are unlike all to Whiteaves claim that his steinkerns (one of the above-mentioned gastropods in one im- with a multispiral operculum) from the Daw- portant aspect. In all of the aforementioned son Bay Formation are at least related to the snails the plane of the aperture is tangent to material from the Winnipegosis Formation, if the preceding whorls (a tangential aperture) not actually conspecific. while in the Omphalocirridae the plane of the In both opercula as seen in place within the aperture transects the axis of coiling of the aperture, the volutions grow outward in a shell (a radial aperture) with the result that a counter-clockwise fashion thus demonstrating great portion of the earlier volutions projects conclusively that Hypomphalocirrus, and by in- beyond the plane of the aperture. This would ference Omphalocirrus, are dextral shells, and seem disadvantageous for a gastropod whose that the canal-like projections are really on aperture is parallel to the plane of the sub- the base of the shell. Thus the orientation of strate. Perhaps the Omphalocirridae have a this enigmatic genus is no longer in doubt and very different relationship to the substrate. In it can finally come to rest, 'spines' down. fact it has been suggested (Linsley and Yochel- However, the solution of the problem of the son, 1973) on the basis of completely different orientation of the shell of the Omphalocirridae, criteria that some euomphalids [Euomphalus is only the solution of the orientation for our (Euomphalus), E. (Straparollus) and E. (Ser- descriptive purposes. Saying that the beast has pulospira)] lived base down with the plane of finally come to rest 'spines down' only relates the aperture perpendicular to the substrate. In to the orientation of figures on a plate for the this position there would no longer be a need purposes of comparative morphology and has for the aperture to be tangent to the preceding nothing necessarily to do with the orientation whorls indeed it seems to a general of the shell to the substrate while the organism and be to the was living. It allows us to invoke the concepts character of most euomphalids have 'dextral', 'sinistral', 'orthostrophic' and 'hyper- plane of the aperture intersect at or near the strophic' and to ascertain homologous por- axis of coiling of the shell. 46 ROBERT M. LINSLEY

This would be an adaptation suitable for a (siphonal) canals of many of the modern sedentary gastropod, perhaps a deposit feeder Caenogastropoda and I propose that they be or even a filter feeder. The organism might called 'inhalent tremata'. Hypomphalocirrus possibly be capable of hoisting his shell into is not unique among Devonian gastropods in the normal position for short journeys to new the development of a portion of the aperture feeding grounds. More probably the shell for a specialized incurrent function. In the would just be dragged along during locomo- Raphistomatinae alone, both Tylozone and tion. It would be expected that the majority of Buechella show well developed siphonal canals the time would be spent with the shell lying and the lower lip of Arlzonella most probably flat on the substrate and the animal largely marks the position of the inhalent currents as withdrawn inside the shell, protruding only does the plethospirid Diplozone. Even in the to obtain food. For such a habit an operculum Euomphalidae, Pleuronotus and Diploconula would be a distinct advantage. have a basal angulation which would most Whether the Omphalocirridae were filter probably result from a mantle fold which feeders and assumed a living position of the would make an incurrent stream more effective shell lying flat on the substrate, or whether they by being localized. were active grazers and thus carried the shell It is probable that the advent of more ad- erect over their back is not Possibly known. vanced and efficient groups during the Devon- the nature of their spines afford might some ian, such as the Neritacea, the Palaeotrochacea clue. and the Paleozygopleuridae, which would prob- his During investigation of the genera Om- ably be more efficient, increased the pressure phalocirrus and Arctomphalus, Yochelson on the older, more conservative groups such (1966, p. 53) remarked that 'the fact that the as the Macluritacea, Euomphalacea and Pleu- spines develop gradually from nodes would rotomariacea. One temporary solution could be to imply seem that they served no vital func- in improvement of the efficiency of water cur- tion'. Close examination of these canal-like rents as evidenced by Omphalocirrus, Hypom- protuberances in Hypomphalocirrus belie that phalocirrus, Tylozone et ah It was a solution statement. As many as ten to twelve growth that apparently was not tried again until the lines are involved in of the making one projec- Pennsylvanian when we find Knightites, Cyclio- tions, the last of which curve backward in a scapha, and Straparollus (Amphiscapha) de- U-shaped fashion, and upward to form the veloping similar canals or angulations. rim of the canal-like projection (see pi. 4, figs. The primary water current in Hypomphalo- 5, 8). The next growth line does not bend up- cirrus thus entered the mantle cavity by way ward but proceeds across the shell along the of the incurrent canals on the base, passed the normal shell contour, bending forward at the osphradium and left gill and then passed out position of the protuberance, thus leaving an of the mantle cavity, past the anus which was opening ('tremata) which I suggest remains undoubtedly located at the angulation formed functional until the appearance of the next pro- by the junction of the upper and outer whorl jection, whereupon it is filled in with secondary faces. In females of //. manitobensis this upper calcite deposits, very much as are the tremata angulation is also equipped with a row of of Haliotis. canal-like projections which mirror the form However, these canal-like projections can- of those on the lower angulation, but which not be called 'tremata', because tremata (as served found in Tremanotis, Polytremaria and the an excurrent rather than an incurrent Haliotidae) are associated with the exhalent function. It is possible that the peripheral un- function and normally mark the position (or dulations in the female H. rugosus are antece- the eventual position) of the anus. In Hypom- dent to this upper row of projections. phalocirrus the basal position of these projec- If the interpretation of the current arrange- tions necessitates that we regard them as in- ment in Hypomphalocirrus given above is cor- halent in function, thus resembling the inhalent rect, this adds support to the concept (Knight, OMPHALOCIRRIDAE 47

Batten, Yochelson, 1960) that the Macluritidae any mass decrease. If the early chambers were and the Euomphalidae suffered a reduction or filled with water, as is most probable, then pre- elimination of the right gill, for there is no mor- sumably the mass of water would closely ap- phological evidence in the shell that a compar- proximate the mass of flesh. Without a siph- ably effective water current would flow over uncle and the complex gas-exchange cells of the right gill which, in Hypomphalocirrus the cephalopods it seems most unlikely that would have to be positioned under the upper there would be any increase in buoyancy whorl face. gained by the secretion of septa in gastropods. Therefore, if the spines are indeed func- The features which are involved in the sexual tional as incurrent modifications, then the shell dimorphism of this family, i.e. size differential, of the Omphalocirridae must have either been collabral ornamentation, differential develop- ment of keel or canals, carried in an upright position or if lying flat on and hyperstrophism, are all present in the substrate with the left side bearing the Liomphalus northi although they are not as fully differentiated in this spines (the 'base') uppermost. This latter posi- species as they tion would thus be 'upside down' compared are in subsequent species. In Liompha- lus northi the males tend to be hyperstrophic, with our normal way of depicting these shells. smaller, with collabral ornamentation on the upper whorl A Summary of Sexual Dimorphism and the face and a keel separating the Evolution of the Omphalocirridae upper and outer whorl faces. The females are more orthostrophic, larger, and have no colla- Our present knowledge of this family would bral ornamentation or keel on the upper whorl suggest that Liomphalus first developed the face. In all cases where I have had a sufficiently diagnostic features of this family and then gave large population to study, I have assumed that rise to two stocks, one European culminating the largest individuals are the females. The in Omphalocirrus and one North American, one exception to this rule is Omphalocirrus furnishing the Hypomphalocirrus lineage. goldfussi. In the six examples I have seen The development of the operculum of this from Germany, those that I have called fe- group has already been fully treated (Yochel- males are indeed the largest individuals. How- son and Linsley, 1972). Evolutionarily the ever, this makes Tolmachoff's specimen from thick operculum of Liomphalus northi is set at Ellesmere Land a male yet this specimen is the the apertural margin, while in Hypomphalocir- largest individual in the entire family. How- rus rugosus and H. manitobensis the operculum ever, as outlined below, I have other reasons is much thinner and drawn well into the aper- for believing that this is a correct interpreta- ture, as far back as one-fourth volution. It also tion, so until someone has had an opportunity tends to be slightly rotated in this genus, which to study a large population of this species I will is a nice adaptation to allow a circular opercu- continue to consider Tolmachoff's specimen as lum to fit snugly inside a slightly elliptical a male. whorl profile. The operculum of Omphalo- In the Middle Devonian members of the cirrus goldfussi is unknown but most probably family, the best indicator of sex is the rela- exists and has not been associated with that tive development of the canal-like extensions, form. the inhalent tremata. In the Rogers City form, The varying reasons for the presence of the female has very well developed, obviously septa in gastropods has also been discussed re- functional, canal-like inhalent tremata on the cently (Yochelson, 1971). In the case of the base. In addition the junction between the Omphalocirridae it seems unlikely that the upper and outer whorl face has developed a septa are for strengthening the shell or for series of undulations that are presumed to act protection against breakage of the early whorls. as a canal, or at least a means of localizing the Rather the septa would appear only to serve excurrent flow. The male generally lacks both the purpose of body shortening. We do not of these traits. The females from the Winni- know if this body shortening would result in pegosis Limestone have developed canal-like 48 ROBERT M. LINSLEY extensions both on the top and bottom of the same selective pressures relative to the sexes in outer whorl face, while the males have inhalcnt Liomphalus as it subsequently had in the more tremata developed only on the base. This highly specialized offspring. would seem an obvious over improvement the The matter of hyperstrophism is also a per- Rogers City Form and is the main reason that plexing problem in the Omphalocirridae. In I consider Hypomphalocirrus rugosus ancestral Liomphalus northi, Omphalocirrus goldfussi to //. manitobensis. As mentioned earlier I and Hypomphalocirrm manitobensis the males believe the basal canals to be incurrent, while are more hyperstrophic than the females. This the upper canals or shoulder mark the posi- leads me to the conclusion that it is not the tion of the anus and is thus essentially excur- mode of coiling that is significant in itself, rcnt. It is presumed that the female needs but the effect the coiling has on the positioning better mantle circulation to enable it to pro- of the outer whorl face. In the genus Hypom- duce the more bulky egg masses. The males in phalocirrus which has a triangular whorl face, both of these cases have less well developed the outer whorl face of female is oriented so aids to water circulation. In H. rugosus the that it is sub-parallel to the axis of the shell. adult males typically have only a keel where This places both inhalent and exhalent portions the incurrent canals of the female are located of the aperture on the very periphery of the and have an even upper shoulder in place of shell, both placed as far from the axis of coil- the undulating shoulder of the female. The ing as possible. If the shell is positioned in a males of //. manitobensis have only a single set recumbent position, inhalent tremata up, then of canals at the incurrent position instead of they are in the perfect position to obtain clean the double set of both incurrent and excurrcnt water while the anus of Hypomphalocirrus ru- found in the females. Thus the entire evolu- gosus would be placed adjacent to the sub- tion of the North American lineage was ac- strate, while excurrent canal of H. manitobensis companied by an improvement of water cir- would be thrust down into the substrate. Pos- culation in the mantle, with the females con- sibly they buried their faces as does the modern sistently better than the males. detritus feeder Xenophora (Shank, 1969, p. 6). A similar situation exists with the European In the case of Omphalocirrus goldfussi and stock of Omphalocirrus goldfussi. In this Liomphalus northi the whorl profile of the species the female has very well developed in- female tends to be more inflated than that of halent canals whereas in the males, the canals the male, presumably to accommodate the arc not always well developed and are fre- bulkier egg masses. The male, on the other quently only suggested by nodal swellings on hand, has a less inflated slightly more angular the basal keel. external whorl profile (the internal whorl cross section being The Australian representative deviates from subcircular). It is possible that these differences dictate the patterns set by its descendents in that the may the hyperstrophic coiling of the male of Liomphalus northi possesses keels males and the ortho-isostrophic coiling of the female. above and below while the female has only the lower keel. However these keels have no ex- The final feature is one that is possessed pression on the inner surface of the aperture by all members of this family and that is col- and therefore may not be functional relative labral ornamentation in the adult males. In all to water currents as are the well-developed members the immature forms have strong col- keels its of descendents. I would suggest that labral ornamentation, but only in the males this is merely a case of pre-adaptation, where is this juvenile feature carried into the adults. the keels of the ancestral form were selected It is probable that this feature serves to for one function (possibly strengthening the strengthen the shell on juveniles and males. It shell) and secondarily proved useful for a is possible that this becomes unnecessary in completely different function (isolating water females because they possess thicker shells, currents). a result it As would not have the but I have no direct confirmation of this from OMPHALOCIRRIDAE 49 actual observations on shells (a particularly Dr Hugh R. McCabe of the Department of difficult task when ninety per cent of the fauna Mines and Natural Resources of the Province studied consists of latex impressions). of Manitoba was most kind in discussing Mani- toba Geology with the author and in accom- Summary and Conclusions panying the author to outcrops of the Winni- pegosis Formation. All four species of the Omphalocirridae, Omphalocirrus goldfussi, Liomphalus northi, The author was first introduced to the Hypomphalocirrus rugosa and H. manitoben- Rogers City Formation of Michigan by Dr sis exhibit considerable dimorphism in their G. M. Ehlers and Dr R. V. Kestling of the University adult shells. The expressed dimorphism is com- of Michigan Museum of Paleonto- pletely consistent with an interpretation of sex- logy. Both of these men have contributed enor- ual dimorphism in that both dimorphs are al- mously to the author's understanding of the ways present in all localities where extensive geology of this area and to his understanding collections have been made and in a more or of the Rogers City Limestone in particular. I less one-to-one ratio. All species except Liom- am deeply indebted for the many hours spent phalus northi are characterized by having func- with them discussing both geological and bio- tional inhalent tremata developed as canal-like logical aspects of this problem. Access to the extensions of the base. These inhalent tremata Calcite Quarry, Michigan Limestone Opera- are consistently better developed in the mor- tions, U.S. Steel Corporation at Rogers City, photypes that have been considered as females Michigan and to the Preque Isle Corporation of the and it is suggested that this is related to the Quarry, formerly Lake Woods Quarry, improved circulation necessary to aerate the north of Alpena, Michigan, managed by Mr bulky egg mass of the females. Roy Hutchinson for a consortium of steel com- panies, has always been graciously granted.

Acknowledgements I would also like to express my deep appre- ciation to have been This study has been made possible by a four former students who series of grants extended to the author by the of great assistance in this problem. Mr John Sloan Foundation and the Colgate Research Cottrell and Mr John Hoffman spent one auspices Council. These grants were awarded for the summer with me under the of a Col- summers of 1967, 1968, 1969, 1970 and for a gate Research Council Undergraduate Re- sabbatical semester of 1971 which enabled me search Participation grant. They were inde- fatigable field workers to go to Australia to study the fauna of the and spent many hours preparing specimens discussing various Lilydale Limestone as represented in the col- and aspects of the problems. Cottrell was also lections at the National Museum of Victoria, able to accompany me to the Manitoba field Melbourne. I am particularly indebted to Mr area near Winnipegosis. Harold B. Edmund Gill and Mr Thomas Darragh of the Lake Dr Rollins and William Arendt also National Museum of Victoria for opening their Mr accom- panied me to the Rogers City area for field facilities and collections to me and for ex- work in addition Rollins of inestimable tending the hospitality of the entire museum. and was value for the photographic work he did on I would also like to thank Dr Gary Batt of Rogers City material. the Department of Zoology, University of the Auckland for assisting with the photography of Dr R. V. Kesling of the University of Michi- the Australian material. gan Museum of Paleontology, Dr G. Arthur For German material of Omphalocirrus gold- Cooper of the U.S. National Museum and Dr fussi I am indebted to Dr Urlich Jux of the Digby McLaren of the Canadian Geological University of Cologne for taking the author to Survey at Ottawa were very kind in giving a number of collecting sites in the Paffrath the author access to the collections of their re- area and making available comparative ma- spective institutions. terial for study. Lastly I greatly appreciate the many hours 50 ROBERT M. LINSLEY

of stimulating discussion of this problem pro- Fagerstrom, J. A., 1961. The Fauna of the Middle vided by Dr John Morton, Department of Devonian Formosa Reef Limestone of South- west Ontario, /. Paleont., 35, no. 1, pp. 1-48, Zoology, University of Auckland, Dr C. M pi. 1-14. Yonge, Department of Zoology, University of Knight, J. Brooks, 1941. Paleozoic Gastropod Geno- Edinburgh and Dr E. L. Yochelson, U.S. types, Spec. Pap. Geol. Soc. America, 32, pp. Geological Survey. 1-510, pis. 1-96. Abbreviations used in this paper are as fol- , 1952. Primitive Fossil Gastropods and lows: USNM—United States National Mu- their Bearing on Gastropod Evolution, Smith- seum, Washington, D.C.; UMMP—University son. Misc. Collns. 117, (13): 1-56, pi. 1-2. of Michigan Museum of Paleontology, Ann Batten, R. L., and Yochelson, E. L., 1960. Treatise on Invertebrate Paleontology Arbor, Michigan; GSC—Geological Survey of (Moore, R. C„ editor) Part I, Mollusca 1. Geo- Canada, Ottawa, Ontario, Canada; NMV— logical Society of America, Inc., Boulder, Colo- National Museum of Victoria, Melbourne, Vic- rado and University of Kansas, Lawrence, Kansas, toria, Australia. xxiii and 351 pp. Koninck, L. G. de, 1881, Faune du calcaire car- References bonifere de la Belgique, 3* partie, Gasteropodes: Mus. roy. H'tstoire nat. Belgique, Ann. sew Anonymous, 1960. Fossils found in Limestone the of paleont., 6, pp. 1-170, pi. 1-24 (Bruxelles). Calcite Quarry of Michigan Limestone opera- Lamy. E., 1937. Sur le Dimorphisme Sexuel des tions of United States Steel Corp. at Rogers Coquilles, Journ. Conchyliol., 81, 283-301. City, Michigan, U.S. Steel Corp. pp. Linseey, Robert Archiac, E. J. A. d\ and E. P. de Verneutl, 1842. M., 1968. Gastropods of the Middle Devonian On the fossils of the older deposits in the Rhen- Anderdon Limestone, Bull. Amer. Paleont., ish Provinces, preceded by a general survey of 54, no. 244, pp. 333-465, pi. 25-39. the fauna of the Palaeozoic rocks, and followed

by a tabular list of the organic remains of the , 1973. Paleoecological Interpretation of the Devonian system in Europe. Trans, Geo!. Soc. Rogers City Limestone (Middle Devonian, Lond.,6; 303-410, pis. 25-37. Northeast Michigan), Contrib. Mus. Paleont. Baillie, Andrew D„ 1951. Devonian geology of Univ. Michigan, 24, no. 11, pp. 119-123. Lake Manitoba-Lake Winnipegosis area: Province and E. L. Yochelson, 1973. Devonian of Manitoba, Dept. Mines & Nat. Resources, Carrier Shells (Euomphalidae) from North Mines Branch, publ. 49-2. America and Germany U.S. Geo!. Surv. Prof. Baker, H. B., 1926. Anatomical Notes on American Paper 824, pp. 1-26, pi. 1-6. Helicinidae, Proc. Acad. Nat. Sci. Phi/a., 78; McCabe, H., 1967. Field Guide to Devonian Out- 35-56. crops of Southwestern Manitoba. Cooper, G. A. and Thomas Pheean, 1966. Strfrigo- McLaren, D. J., 1963. Southwestern Ellesmere Is- cephalus in the Devonian of Indiana, Smithson land-Goose Fiord to Bjorne Peninsula, p. 310- Misc. Collns., 151(1): 1-20, pis. 1-5. 338 in Fortier, Y. A. and others: Geology of Cox, L. R. and J. B. Knight, 1960. Suborders of the North-Central part of the Arctic Archi- Archaeogastropoda: Proc. Malac. Soc. Loni» 33 pelago, Northwest Territories (operation Frank- (6): 262-264. lin), Mem. Geol. Surv. Canada, 320. CuviER, Georges, 1797. Tableau elcmentaire de Milne Edwards, Henri, 1848. Note sur la classifica- I'histoire naturelle des animaux: xvi + 710 p tion naturelle des moilusques gasteropodes, Ann. 14 pJ. (Paris). Sci. Nat., ZooL, ser. 3, 9, pp. 102-112 (Paris). Ehlers, George M. and Robert V. Kesling, 1970. Philip, G. M. and L A. Talent, 1959. The gastro- Devonian Strata of Alpena and Presque Isle pod genera Liomphalus Chapman and Scalaetro- Counties, Michigan. Michigan Basin Geological chus Etheridge, /. Paleont. 33, pp. 50-54. Society Guide Book for Field Trips. Michigan Robertson, Robert, 1971. Sexually Dimorphic Basin Geological Society, pp. 1-130, pis. 1-38. Archaeogastropods and Radulae, Annual Re- Ehlers, George M. and Robert E. Radabaugh, ports for 1970 of the American Malacological 1938. The Rogers City Limestone, A New Middle Union, pp. 75-78. Devonian Formation in Michigan, Pap. Michigan Ryckholt, P. de, 1860. Revue des generes qui com- Acad. Sci., Arts, Letters, XXIII. pp. 441-446 posent la famille des Haliotidae, D'Orbigny, pis. ML Jour. Conchyliol., 2e ser. 4, pp. 183-188. Etheridge, R. Jr., 1890. Descriptions of Upper Silu- Shank, Paul, 1969. The Timorous Carrier Shell, rian fossils from the Lilydale Limestone, Upper Close Observation of the Xenophora conchvlio- District, Yarra Victoria. Rec. A ust. Mas., 1, no phora Born. New York Shell Club Notes 151 3, pp. 60-67. PP. 5-7. OMPHALOCIRR1DAE 51

Sohl, Norman F., 1969. Gastropod Dimorphism, in (xl) exhibiting strengthening of collabral Westermann, G.E.G. editor, Sexual Dimorphism ornamentation near the suture. on Fossil Metazoa and Taxonomic Implications, Figure 6—Apical view (xll) of paratype USNM Intern. Union of Geol. Sciences, Ser. A, 1, pp. 213769 from the Miami Bend Formation 94-100. in Ohio. Strusz, D. L., 1972. Correlation of the Lower De- Figure 7—Apical view (xl-75) of paratype USNM vonian Rocks of Australasia. /. Geol. Soc. Aits*. 213770. In this specimen the collabral or- 18(4): 427-455. namentation is very strong in the youth- Tassell, C. B., 1976. A Revision of the Gastropod ful stage and becomes diminished with Fauna of the Lilydale Limestone (Early Devon- increasing age. ian) of Victoria, Mem. Natn. Mus. Vic. 37: Figure 8—Apical view (x0-75) of paratype USNM 1-21. 213762. Again the collabral ornament be- Thiele, Johannes, 1925. Mollusca—Weichtiere: comes weaker with increased age. Handbuch der Zoologie, gegriindet W. Kuken- Figure 9—Cross-section (xl-4) of paratype USNM thal, 5, pp. 15-256 (Berlin, Leipzig). 213763 showing numerous irregularly Tolmachoff, I. P., 1926. On the fossil faunas from spaced septa. Per Schie's Series D from Ellesmere Land with exception of brachiopods, corals, and cephalo* PLATE 3 pods: Report the second Arctic of Norwegian Hypomphalocirrus rugosus n. sp. All figures are of expedition in the Tram' 1898-1902, 38, pp. males from the Rogers City Limestone. 1-106, 8 pis. Figures 1, 11 Oblique basal (xl-5) and basal (x0-8) Whiteaves, J. F., 1890. Descriptions of some new or — views of Paratype, USNM 102939 show- previously unrecorded species of fossils from the ing flange-like projections of early whorls Devonian rocks of Manitoba, Trans. R. Soc. giving way to a continuous keel on the Canada, VIII, sec. 4, no. 3, pp. 93-110. ultimate whorl. , 1892. The fossils of the Devonian Rocks Figure 2 Apertural view of Paratype USNM of the islands, shores, or immediate vicinity of — 213777 (xO-75). Lakes Manitoba and Winnipegosis, GeoL Surv. Figure 3-—Basal view (x0-65) of Paratype USNM Canada, Contrib. to Cana. Paleont., 1, pt. 4, no. 213757. Note continuous keel on ultimate 6, pp. 255-359, pis. 33-47, Ottawa. whorl. Yochelson, E. L., 1966. A Reinvestigation of the Figure 4 Adapertural view (0-6) of Paratype Middle Devonian gastropods Arctomphalus and — USNM 213779 showing slight suggestion Omphalocirrus, Arbok norsk Paralinst. 1965, pp. of a spiral groove just below the shoulder. 37-48. Figure 5—Oblique basal view (xO-6) of Paratype , 1971. A new Upper Devonian gastropod USNM 213766 very large male with un- and its bearing on the problems of open coiling usually well developed flange-like projec- and septation, Smithsonian Contr. Paleobiology, tions on the base. 231-241, pis. 1,2. 3, pp. Figure 6—Oblique basal view (x0-6) of Paratype and R. M. Linsley, 1972. Opercula of two USNM 213773 showing well developed gastropods from the Lilydale Limestone (Early spiral groove just below shoulder. Devonian) of Victoria, Australia, Mem. Natn. Figure 7—Basal view (x0-9) of Paratype USNM Mus. Vict. 1-14, pis. I-II. 33, pp. 213774. Figure 8—Apical view of Paratype USNM 213775 (x0-6) showing well developed colla- Explanation of Plates bral ornamentation. Figure 9 Oblique basal view (xO-9) of Paratype PLATE 2 — USNM 213778. Note sharp single keel n. sp. figures of Hypomphalocirrus rugosus All are on base and smooth outer whorl face. Figure from the males. All specimens except 6 Figure 10—Basal view (xO-9) of Paratype UMMP Rogers City Limestone. 57889, a mature specimen with well- Figures 1-3 —Basal, apical and apertural views (xl-8) developed keel and deep umbilicus. of paratype UMMP 22384, from the Figure 12, 14—Basal (xO-9) and oblique basal (xO-8) beach at Rockport Note flat upper sur- views of Paratype, USNM 213761. This face, strong collabral ornamentation and specimen is unusual because of the round- 45° inclination of outer whorl face. ness of the base. Note also the well- Figure 4—Apertural view of paratype USNM 213775 developed flanges and the strong collabral (xO-75) showing subtriangular whorl pro- ornamentation. file with flat upper whorl face and in- Figure 13 —Basal view (xO-6) of mature specimen, clined outer whorl face. Paratype USNM 213756 with a rounded Figure 5—Apical view of paratype, UMMP 22383 base with no flanges or keel. 52 ROBERT M. LINSLEY

Figure 15—Basal view (xO-6) of Paratype USNM PLATE 6 213780. Hypomphalocirrus rugosus n. gen. and sp. All figures of females from the Rogers City Limestone. PLATE 4 Figures 1, 8—Oblique basal (x0-7) and apertural Hypomphalocirrus rugosus n. gen. and sp. All figures (xl-25) views of Paratype UMMP 22379. are of females from the Rogers City Limestone. A thin individual with undulating shoul- Figures 1,2, 5, 6, 8—Oblique apical (xO 6), apertural der, flanges and roughened outer whorl (x0-8), basal (x0-8), apical (xO-8) and face. oblique basal (xO-8) of holotype UMMP Figure 2—Apertural view (xO 6) of Paratype 22377. A very large mature female show- UMMP 22378 showing strong hyperstro- ing well-developed basal flanges, undulat- phism. ing shoulder, high degree of hyperstro- Figure 3 —Oblique basal view (x0-5) of Paratype phism and rugose, near vertical outer USNM 213759 with an unusually high whorl face, all typical features of the outer whorl face. adult female. Figure 4—Oblique basal view (xO-8) of Paratype Figure 3—Apical view (xO-6) of paratype UMMP USNM 213772 showing well-developed 22378 showing smoothness of early undulations on shoulder and the rugose whorls and the undulating shoulder. outer whorl face. Figure 4—Outer surface (xl-25) of operculum, para- Figure 5 —Apical view (xO 9) of Paratype USNM type USNM 213768 showing the multi- 213781. This specimen is a female on the spiral form typical of the opercula of this basis of its hyperstrophism, but exhibits family. the male characters of strong collabral Figure 7—Oblique apical view (xO-75) of Paratype ornamentation and smooth shoulder. USNM 213758, the most extremely hyper- Figure 6—Oblique basal view (x0-7) of Paratype strophic individual in the entire collec- USNM 213776 showing strong flanges on tion. base and undulating shoulder. Figure 7—Oblique apical view (xO 75) of Paratype, PLATE 5 USNM 213765 showing exceedingly ru- gose outer whorl face- Hypomphalocirrus rugosus n. gen. and sp. All figures Figure 9 Basal view are of females from the Rogers City Limestone. — (xO 6) of Paratype UMMP 22380. This specimen Figure 1—Apical view (xO-75) of Paratype, USNM has an unusually round whorl profile and thus greatly re- 2 1 3755. Note the degree of hyperstro- sembles Omphalocirrus goldfussi. phism and undulating shoulder on this Figures 11 large specimen. 10, —Oblique apical (x0-7) and oblique basal views Figure 2—Oblique basal view (x0-7) of Paratype, (x0-9) of Paratype, USNM 213754 showing USNM 213764 showing well-developed rugose outer whorl face projecting flanges. and very strong undulating shoulder. Figure 3—Basal view (x0-85) of Paratype USNM PLATE 7 213760. This mature specimen illustrates the well-developed basal flange-like pro- Hypomphalocirrus manitobensis (Whiteaves) trusions of the female, but the collabral Figure 1—Oblique apical view (xl-8) of Hypotype, ornamentation is better developed than is USNM 213783 showing operculum set of typical. an oblique angle inside the ultimate whorl. Figure 4 Apical view (xO-6) of Paratype — UMMP Coiling of multispiral operculum indicates 57888. This very large female has only this is orthostrophic coiling. moderate hyperstrophism and no develop- Figures 2, 4—Whiteaves cotype, GSC 4174. The ment of the undulating shoulder. break in this steinkern marks the position Figure 5—Basal view (xl-0) of Paratype USNM of the operculum. This operculum is 213767 showing strongly developed, placed at a greater angle to the axis of spade-like basal flanges. the whorl than that found in Fig. 1, in- Figure 6—Apical view (xl-1) of Paratype UMMP dicating that there was some rotation after 22379, showing undulating shoulder. death. Figure 7—Apical view (x3 0) of Paratype 3 UMMP Figure —Oblique basal view of Whiteaves Plesio- 22375. Very immature specimens such as type GSC 4176, a female showing full this are very difficult to sex. This in- development of both rows of spines. Also dividual has the degree of hyperstrophism note rugose outer whorl face. which suggests a female, but the well- 8 Figures 5, 6, —Apertural, basal and apical views of developed collabral ornamentation sug- Whiteaves Plesiotype GSC 4177a. Note gests a male. the two rows of spines and the pseudo- i

OMPHALOCIRRIDAE 53

isostrophic coiling typical of the female. Figures 1-3 —Apical, basal and apertural views (x2) Figure 7—Basal view of hypotype USNM 213782, of an immature female Hypotype NMV an immature male showing well-developed P28716, At this young age the females basal inhalent tremata, collabral orna- exhibit many of the male characters such mentation and hypertrophic coiling. as collabral ornament and a faint keel on top as well as bottom. Note however that PLATE 8 it is orthostrophic rather than hypertro- All figures of Omphalocirrus goldfussi (Archiac and phic as is the case with the males (cf. PI. Verneuil) 10, Fig. 5). Figure 4 Apical view (xO-7) of Hypotype Figures 1, 2, 9—Oblique basal (xO 8), basal (xO-75) — NMV P28709, and apical (xO-7) of latex cast (from showing rounded upper whorl face with USNM) of topotype figured by Knight no keel and no collabral orna- ment. (1941) of a specimen from the Puzo Col- 8 lection, Ecole de Mine. This specimen is Figures 5, 7, —Oblique apical, apical and basal presumably a female characterized by views (xO-7) of Hypotype, NMV P28711, being orthostrophic and having well-de- a large female showing strong keel and veloped inhalent tremata present through- collabral ornamentation on the base and out its growth. no keel and no collabral ornamentation on the top. Figures 3, 6—Basal (xlO) and oblique basal (xO-8) views of latex cast (from USNM) of Figures 6, 9, 10—Oblique apical (xO-7), basal and Holotype which is housed in the De Ver- apical (x0-5) views of Hypotype, NMV neuil Collection at the Ecole national P28712. superieure des Mines, Paris, France. This Figure 11 —Cross section (xO-7) of Hypotype, NMV is presumably a female showing the weak P28499 showing septal filling of early collabral ornamentation of the base. whorls. Figures 4, 5—Oblique basal and basal views (xl-8) Figures 12, 13 —Basal (xO-8) and apical (xl) views of a plaster cast (from USNM) of a of Hypotype NMV P28708. specimen from Sotenich, Germany, Strin- Figures 14, 17—Basal and apical views (xO-7) of gocephalus Limestone (Givetian). The Hypotype, NMV 28498. Note flat spire original of this specimen is from Hum- and depressed umbilicus. boldt Universitat, Berlin, Germany. This Figures 15, 16—Basal and apical views (xO-5) of Hy- is presumably a male and is thus hyper- potype, NMV P28373, the largest speci- strophic, with non-functional inhalent tre- men in the collection. mata and strong collabral ornamentation of the base. PLATE 10 Figure 7—Basal view (xl-0) of plaster cast (from USNM) of holotype of 'Arctomphahis Liomphalus northi (Etheridge). All figures of males grandis* TolmachofT, 1926, specimen No. from the Lilydale Limestone, Cave Hill Quarry, Lily- A 19229 in the Paleontologist Museum of dale, Victoria, Australia. Oslo, Norway. The total size of this Figures 1-3 —Apical, basal and oblique apical views specimen is indicated by the dashed line, (xl) of Hypotype, NMV P28714, a typi- but the adult whorls are only represented cal male showing collabral ornamentation by a steinkern. The inner whorls indicate and keel on both top and bottom. Also the features typical of the male Omphalo- note the degree of hyperstrophism. cirrus. Figures 4-6—Apical, apertural and basal views (x2) Figure 8—Basal view (xLl) of plaster cast (from cf Hypotype NMV P28719. This is a USNM) of a specimen from Vilmar, small male showing the degree of hyper- Germany. Upper Stringocephalus zone. strophism typical of the males. The original of this specimen is in the Figure 7—Basal view (xl) of Hypotype NMV Humboldt Universitat, Berlin, Germany. P28707 showing very strong basal keel. This specimen is hypertrophic and shows Figures 8, 11 —Apical and oblique views (xO-7) of the other male characters of incipient Hypotype, NMV P28717. On this strongly nonfunctional inhalent tremata and hyperstrophic male the upper keel be- strong collabral ornamentation. comes lost on the ultimate whorl, but the collabral ornament continues all of the PLATE 9 way. Liomphalus northi (Etheridge). All figures of females Figures 12, 17—Apical (xO 9) and basal views (xl) from the Lilydale Limestone, Cave Hill Quarry, Lily- of Hypotype, NMV P28713. This male is dale, Victoria, Australia. unusual for though it is markedly hyper- 54 ROBERT M. LINSLEY

strophic it has lost the keel and collabral Figure 14—Apical view (xO-7) of Hypotype, NMV ornament on the top. P28710.This specimen still has the keel 6 Figures 13, 1 —Apical (xl ) and oblique apical on top, but has lost the collabral orna- (xO 7) views of Hypotype, NMV P1107. mentation. This large male exhibits all of the typical Figure 15—Apical view (xO 7) of Hypotype, features: keel and collabral ornamenta- NMV 28718. This crushed male shows tion top and bottom, and hyperstrophism. strong collabral ornamentation and well- Note massive, multispiral operculum in developed keel. place in the aperture.

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80 70 60

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Figure 1 —A plot of shell width on the abscissa ver- sus the width of the umbilicus divided by the depth of the umbilicus, a sensitive measure of the degree of hyperstrophicity. Note that in the larger individuals the cloud of points divides into two groups of about equal numbers. This is considered ,30 iao wo as strong evidence in favour of sexual SHELL WIDTH (mm) dimorphism. MEM. NAT. MUS. VICT. 39 PLATE 2

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