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Home , Acanthochitonidae, Ampullina, Anatoma, Angaria (gastropod), Angaria delphinus, Arene (gastropod)

Chitons and Gastropods (Haliotidae Through Adeorbidae) From the Western Pacific

GEOLOGICAL SURVEY PROFESSIONAL PAPER 531 and Gastropods (Haliotidae Through Adeorbidae) From the Western Pacific Islands

By HARRY S. LADD

GEOLOGICAL SURVEY PROFESSIONAL PAPER 531

Description and preliminary paleoecologic in­ terpretations of moll usks from seven groups

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1966 UNITED STATES DEPARTMENT OF THE INTERIOR

STEWART L. UDALL, Secretary

GEOLOGICAL SURVEY

William T. Pecora, Director

Library ut' Oongivw, catalog-curd Xo. GS 66-257

For sale by the Superintendent of Documents, U.S. Government Printing Office Washington, D.C. 20402 - Price $1.25 (paper cover) CONTENTS

Page Page Abstract ______- 1 Paleontology Continued Introduction - 1 Paleoecology ____ 11 and localities 1 Faunal relations _ 15 Purpose and scope ____ .. - 1 Systematic paleontology . 20 Earlier references to fossil mollusks ______3 Chitons ______- 21 Palau ______- 3 Schizochitonidae _ _ 21 Mariana Islands ______3 ______23 Marshall Islands ______3 _ ___ 24 Ellice Islands ______3 Gastropods ______25 Funafuti ______. 3 Haliotidae _ 25 .. 26 New Hebrides ______3 ______27 ______4 ______-_ 32 Tonga ______5 ______-__ - 33 Collections ______5 Stomatellidae ______. 41 Acknowledgments ______-______6 Angariidae (Delphinulidae) 42 Geology ______6 ______- 43 Stratigraphy ______. 6 ______53 Eocene ______. Neritopsidae ______55 ______Neritidae ______- 55 Miocene ______. _ 59 ______59 Post-Miocene ______. ______60 ______. .______. 9 ______. 75 Pleistocene and Recent .______. 9 Adeorbidae () ______75 Correlation ______. .______. 9 Localities ______81 Paleontology ______9 References ______89 Geographic and geologic distribution of _____ 9 Index ______93 ILLUSTRATIONS

[Plates follow index") PLATE 1. Chitons. Page 2-16. Gastropods: FIGURE 3. Sketch map of Guam, Mariana Islands, showing 2. Haliotidae, Scissurellidae, and Fissurellidae. localities mentioned in text ______82 3. Fissurellidae, Patellidae, and Trochidae. 4. Sketch map showing fossil localities on 4. Trochidae. Haipan, Mariana Islands __. 83 5. Trochidae, Stomatellidae, and Angariidae. 5-8. Maps showing locations of drill holes: 6-9. Turbinidae. 5. Eniwetok ______84 10. Phasianellidae, Neritopsidae, , and 6. Eniwetok Atoll ______85 Assimineidae. 7. Bikini Atoll ______. 86 11. Neritidae, Littorinidae, Iravadiidae, and Rissoidae. 8. Funafuti Atoll ______86 12,13. Rissoidae 9-14. Maps showing fossil localities: 14. Rissoidae and Adeorbidae. 9. New Hebrides ______87 15, 16. Adeorbidae. 10. Viti Levu, Fiji _____ . 87 11. Fulanga, Lau, Fiji ____ . Page FIGURE 1. Index map showing location of island groups _ 2 12. Ongea, Lau, Fiji ____ . 2. Sketch map showing fossil localities in the 13. Lakemba, Lau, Fiji __ . 89 Goikul area, Palau ______81 14. Tongatabu, Tonga ______89

TABLES

Page TABLE 1. Distribution of Cenozoic sediments in the island area ______7 2. Major stratigraphic subdivisions recognized in holes drilled in the Marshall Islands______7 3. Correlation of Cenozoic units in the island area ______10 4. Geographic distribution of species ______12 5. Geologic distribution of species ______. 16 6. Living Lido-Pacific mollusks that also occur in the upper Tertiary sediments of the island area 20 CHITONS AND GASTROPODS (HALIOTIDAE THROUGH ADEORBIDAE) FROM THE WESTERN PACIFIC ISLANDS

By HARRY S. LADD

ABSTRACT during the Miocene. Ties between the island area and the Cenozoic mollusks from seven island groups in the western Americas are suggested, but they are less impressive than rela­ Pacific are treated systematically. The islands form a broad belt tionships with the Indo-Pacific. spreading 4,000 miles across tropical latitudes from the Mariana Islands and Palau on the northwest through the Marshall, Ellice INTRODUCTION and New Hebrides groups to Fiji and Tonga on the southeast. Each of the island groups has a section of limestones AREA AND LOCALITIES and all except the Ellice group are known to have a Tertiary The islands of the western Pacific considered here sequence as well. The known Tertiary in all island groups, except form a broad and somewhat irregular belt spreading that in the New Hebrides, extends back as far as the Eocene. No rocks have been recognized. 4,000 miles across the tropical latitudes of the western Two hundred and eight species and subspecies are described. Pacific, from the Mariana Islands and Palau on the These include representatives of 3 families of chitons and 16 northwest to Fiji and Tonga on the southeast (fig. 1). families of gastropods (Haliotidae through Adeorbidae). Three The belt measures approximately 1,000 miles in width new subgenera of gastropods are described: Vitiastraea (sub- and includes seven island groups Marshall,- Ellice, of Astraea), Subditotectarius (subgenus of ), and Mariana, Palau, New Hebrides, Fiji, and Tonga. Of Ailinzebina (subgenus of Zebina). Sixty-seven new species and five new subspecies are described. The species discussed in the these, only the Marshall and Ellice Islands lie in the present report comprise approximately one-sixth of available Pacific Basin proper, within the circum-Pacific 'andesite collections. line. As thus outlined, the belt includes all of Micronesia About three-fourths of the new forms were recovered from the and eastermost Melanesia and separates from drill holes in the Marshall Islands; the remainder, from outcrop most of the Pacific Basin proper. samples, are divided almost equally between Palau and Fiji. A few of the new forms from the Marshall Islands also occur in Palau and Fiji. PURPOSE AND SCOPE The richest and most widespread assemblages are Miocene This primarily paleontologic report deals mainly with (Tertiary / and g). Most of the mollusks are associated. large collections of fossil mollusks obtained by the U.S. Many, notably those of the limestones in the deep drill holes of the Marshall?, occur in beds that were deposited in ; Geological Survey and other governmental agencies dur­ some species occur in beds that were accumulated on tidal flats; ing field investigations in Micronesia in the years im­ a few species lived in fresh or brackish waters. mediately following World War II. These investigations The assemblages of fossil mollusks, like those living in the were of two types: (1) Deep drilling at Bikini Atoll in area today, are Indo-Pacific in general aspect. The strongest dis­ connection with Operation Crossroads in 1947 and at cernible ties are with living and fossil faunas of tropical Indo­ Eniwetok Atoll for the Atomic Commission in nesia, rather than with faunas from more southerly (south­ ern and ) or more northerly areas (the 1951-52; all deep drilling was under the supervision of Ryukyu Islands and Japan). Thirty-throe of the des-ribed species U.S. Geological Survey personnel. (2) Detailed mapping that still live in the island area have been there at least since projects carried on by the U.S. Geological Survey under late Tertiary . Of this group, the shells of 25 were recovered the sponsorship of the U.S. Army, Corps of Engineers, from Marshall Island drill holes, those of 10 from outcrops in in Palau, 1947-48, Saipan, 1948-49, Tinian, 1949-51, and Fiji. A few species that lived in the island area during the Guam, 1951-54. The Survey's collections from Guam Tertiary are now living only in other parts of the Indo-Pacific region. supplement even larger collections made earlier by the Numerous living Indo-Pacific species had close relatives, some Pacific Island Engineers under contract with the U.S. perhaps ancestral, in the island area during the upper Tertiary. Navy. In the Miocene of Bikini is a species of Pisulina, a genus known In an attempt to make the study of island fossil mol­ previously only from a few species living near India and Ceylon. lusks as complete as possible, collections from other The neanvt relatives of a lower Miocene CtjniNcn of Eniwetok live off the Capo of Ciood Hope, South , tichtzachitott, the island groups Fiji, Tonga, New Hebrides, and Ellice reef that lives today in the and northern Aus­ Islands have been reviewed. Some material from these tralia, had representatives in the Marshall Islands and Palau islands, already described in print, has been reexamined. CHITONS AND GASTROPODS FROM WESTERN PACIFIC ISLANDS

FIGTRK 1. Location of island groups from which fossil mollusks have been obtained. Dashed line marks structural boundary of Pacific Basin (andesite line).

The mollusks living in the western Pacific island area ments of age, correlation, and paleoecologic interpreta­ today are closely related to those of Indonesia, and a tion are given in this paper, but a full discussion of these study of fossil forms should have some bearing on ques­ matters and detailed interpretations of regional relations tions involving origin and migration. Preliminary state­ of the faunas arc reserved for a later paper. INTRODUCTION

EARLIER REFERENCES TO FOSSIL MOLLUSKS 1960. Ladd, H. S., Origin of the Pacific Island molluscan fauna: Am. Jour. Sci., Bradley volume, 258-A, p. 137-150. Published papers that contain identifications or de­ scriptions of fossil mollusks from the island under con­ Summarizes data supporting a suggestion that many elements of the Indo-Pacific fauna may have originated sideration are briefly annotated and arranged chron­ in the islands in and Tertiary and ologically under island groups below. later migrated with aid of prevailing winds and currents to west and southwest. PALAU 1960. Ladd, H. S., and Schlanger. S. 0., Drilling operations on 1951. Hatai, Kotora, Fossil from Angaur Island: Inst. Eniwetok Atoll. U.S. Geol. Survey Prof. Paper 260-Y, Geology and Paleontology, Tohoku Univ., Short paper p. 863-903. 3, p. 127. Includes generic identifications of mollusks in series Collections made by R. Tayama contain a dozen of drill holes, deepest of which reached upper Eocene forms. Five are identified with Recent species, and it (Tertiary b). is concluded that the beds are probably post-Miocene in age. 1960. Ladd, H. S., Distribution of molluscan faunas in the Pa­ MARIANA ISLANDS cific islands during the Cenozoic: U.S. Geol. Survey Prof. Paper 400-B. p. B374-B375. 1956. Gardner, Julia, in Cloud, P. E.. Jr., Schmidt, R. G., and Burke, H. W., Geology of Saipan, Mariana Islands: Brief summary of known occurrences of fossil mol- U.S. Geol. Survey, Prof. Paper 260-A, p. 47, 60, 66-67, lusks in six island groups in the western Pacific. 80-81, 86-87. ELLICE ISLANDS Preliminary reports on collections of fossil mollusks FUNAFUTI from Tertiary and younger rocks of Saipan. From the Eocene (Hagman Formation and Matanzas Limestone) 1904. Hinde, G. J., Report on the materials from the borings a few generic references; from the Miocene (Tagpochau at the Funafuti Atoll, in The Atoll of Funafuti: Royal Limestone) 29 mollusks named, 13 being specifically Soc. London, p. 187-361. identified or compared with named species; from the A few of the obtained from the upper parts of Pleistocene (Mariana and Tanapag Limestones) 30 mol­ the drill holes contain rare but well-preserved shells of lusks, of which 19 are identified specifically or compared , and many of the cores from lower levels with described species. Molluscan fauna of Mariana show molds of larger mollusks. A few generic determi­ Limestone probably represents older Pleistocene. nations made by E. A. Smith and others are cited, but in most places molluscan occurrences are recorded merely MARSHALL ISLANDS as casts of gastropods or lamellibranchs. 1954. Ladd, H. S., in Emery, K. 0., Tracey, J. I., Jr., and Ladd, H. S., Geology of Bikini and nearby , Marshall 1957. Ladd, H. S., and Tracey, J. I., Jr., Fossil land shells from Islands: U.S. Geol. Survey Prof. Paper 260-A. p. 80- deep drill holes on western Pacific atolls: Deep-Sea 84, 90. Research, v. 4, no. 3. p. 218-219. Fossil mollusks from seven intervals in upper 300 Cites occurrence of species of Ptychodon in sample feet in deep drill holes identified with species living in obtained from holes drilled in post-Miocene reefs. existing lagoons of Bikini and Eniwetok. Mollusks from 925 to 935 feet recognized as appreciably older shallow- 1958. Ladd, H. S., Fossil land shells from western Pacific Islands: water fauna. Jour. Paleontology, v. 32, no. 1, p. 183-198. Ptychodon sp. A is described and figured from par- 1957. Ladd. H. S., and Tracey, J. I., Jr., Fossil land shells from dally leached coralliferous limestone from a drill hole deep drill holes on western Pacific atolls: Deep-Sea at a depth of 166-170 feet. Age, Pleistocene or Recent. Research, v. 4, no. 3, p. 218-219. Records occurrence of four species of minute land NEW HEBRIDES in Miocene and younger rocks of atolls, including 1905. Mawson, Douglas, The geology of the New Hebrides: Bikini and Eniwetok. Because the shells belong to a Linnean Soc. Proc., v. 30, p. 400-485. genus (Ptychodon) that normally lives on forested is­ lands well above sea level, their occurrence suggests Includes reference (by number) to occurrences of that the present-day atolls periodically stood above sea fossil mollusks identified by and listed level, functioning as stepping stones in the distribution in appendix. of life. 1905. Hedley. Charles. Determinations of Mollusca, in Mawson, 1958. Ladd, H. S., Fossil land shells from western Pacific atolls: Douglas, The geology of the New Hebrides: Linnean Jour. Paleontology, v. 32, no. 1, p. 183-198. Soc. New South Wales Proc., v. 30, p. 477-478. Descriptions of fossil endodont land snails (Ptycho­ Lists 82 generic and specific determinations of mol­ don) including three species obtained from Bikini and lusks believed to range in age from Pliocene to Recent. Eniwetok from lagoonal deposits now 170-1800 feet be­ Several are considered to be new but are not described. low sea level. Ages ranges from Miocene (Tertiary e) Some forms thought to have lived beyond intertidal to Pleistocene or Recent. levels, perhaps as deep as 15 fathoms. CHITONS AND GASTROPODS FROM WESTERN PACIFIC ISLANDS

1937. Abrard, Rene, and La Rile, E. A. de, Sur 1'existence du 1903. Woolnough, W. G., The continental origin of Fiji: Linnean Neogene superieur a Cycloclypeus aux iles Epi et Male- Soc. New South Wales Proc., v. 28, p. 457-540. kula (Nouvelles-Hebrides): Acad. sci. [Paris] Comptes 1907. Woolnough, W. G., A contribution to the geology of Viti i-emhis, v. 204, no. 25, p. 1951-1953. Levu, Fiji: Linnean Soc. New South Wales Proc., v. Nine fossil mollusks are identified with Recent Indo- 32, p. 433-474. Pacific species, four with fossil forms described by Ladd Though Woolnough collected no specifically identifi­ from Viti Levu, Fiji, two with Miocene species from able fossil mollusks, he records the occurrence of frag­ Java; 17 others appear to be undescribed. mentary shells of Conus and Pecten, believed to be 1937. Abrard, Rene, and La Rile, E. A. de, Sur la presence du Tertiary, at localities in the then little known interior Pliocene a Tile Malekula (Nouvelles Hebrides): Acad. of Viti Levu. [These clues led later workers to well- sci. [Paris] Comptes rendus, v. 205, no. 4, p. 290-292. preserved molluscan faunas. H.S.L.] A total of 31 mollusks are identified with Recent 1903. Guppy, H. B., Vanua Levu, v. 1, oj Observations of a species or compared with such forms. Three others are naturalist in the Pacific between 1896 and 1899: Mac- recognized as new, and three are identified with species millan and Co., 392 p. from the Pliocene of Java. The beds are assigned to the Pliocene. Generic identification given for pelecypods in shell bed elevated a few feet above the sea, in limestones and 1938. Abrard, Rene, and La Riie, E. A. de, Note sur les depots in tuffs, some of the tuffs now lying more than 2.000 Quaternaires et les recif s souleves du Nouvelles-Hebrides: feet above sea level. Soc. geol. France Bull., v. 8, p. 63-66. 1918. Foye, W. G., Geological observations in Fiji: Am. Acad. Twenty-five generic and specific identifications of Arts and Sci. Proc, v. 54, no. 1, p. 1-142. mollusks are reported from elevated limestone on Efate; age probably Quaternary but possibly Pliocene. Nine­ On page 86 there is a list of 15 generic identifications teen mollusks are listed from similar limestones on of mollusks as made by Paul Bartsch; the genera are Eromanga. common tropical forms, each being followed by a query; Foye collected the material from three localities on 1946. Abrard, Rene, Fossiles Neogenes et Quaternaires des Nou­ Viti Levu. velles-Hebrides: Annales de paleontologie, v. 32, 112 p., 5 pis. 1926. Mansfield, WT . C., from quarries near Suva, Viti Levu, Fiji Islands * * * with annotated bibliography of Detailed and well-illustrated report on large collec­ the geology of the Fiji Islands: Carnegie Inst. Wash­ tions of mollusks (126 species) and other fossils made by ington Pub. 344, p. 85-104. E. A. de La Riie from Miocene and later rocks at Malekula, Epi, Efate, and Eromanga. Close ties estab­ Description of 4 gastropods and 14 pelecypods (in­ lished to Miocene of Fiji. cluding 3 new species). Tertiary age suggested, prob­ ably late Miocene or early Pliocene. FIJI 1927. Matley, C. A., and Davies, A. M., Some observations on 1880. Woods, J. E. T., On some fossils from Levuka, Viti: the geology of Viti Levu: Geol. Mag. [Great Britain], Lmnean Soc. New South Wales Proc., v. 4, p. 358-359. v. 64, no. 752, p. 65-75. Several fossils, including mollusks, said to have been collected from the center of Ovalau, exact locality un­ Includes description of supposed fresh-water , Nodularia vitiensis Davies, from the marls above known. No specific identifications were made, but some of the mollusks were compared with Miocene species Nasongo; beds probably Tertiary, possibly Miocene. of Australasia. The fossils were imbedded in clay and 1930. Davies, A. M., Fossils from Viti Levu: Geol. Mag. [Great sandy clay. [No rock of this type has been reported Britain], v. 67, no. 787, p. 48. from Ovalau. and it seems probable that the material was collected from the marls of nearby Viti Levu. Molds of bivalves from near Nasongo, referred in H.S.L.] 1927 (Matley and Davies) to the fresh water clam Nodularia, are reassigned to marine Mactracea. 1898. Ball, W. H., in Agassiz, Alexander, The Tertiary elevated limestone reefs of Fiji: Am. Jour. Sci., 4th ser., v. 6, 1934. Ladd, H. S., in Ladd and others, Geology of Vitilevu, p. 165. Fiji: B. P. Bishop Mus. Bull. 119, 263 p. Contains identification of examples of 10 still-living One hundred and twenty-two mollusks (53 pelecypods, genera of mollusks. Expresses the belief that the rock 3 scaphopods, 1 chiton, and 65 gastropods), most of which is probably younger than Eocene, possibly Miocene or were collected during reconnaissance surveys in 1926 Pliocene. and 1928. are described and most of them figured; they are from beds ranging in age from Miocene to Recent. 1900. David, T. W. E.. Preface to geological report by E. C. Brief discussion of paleoecological conditions. Andrews: Harvard Coll. Mus. Comp. Bull., v. 38, p. 5-10. 1945. Ladd. H. S., in Ladd and Hoffmeister, J. E., Geology of Mentions occurrence of large Tridacna in conglomerate Lau, Fiji: B. P. Bishop Mus. Bull. 181, 399 p. exposed at Walu on Viti Levu that suggests an Seventy-six mollusks, half pelecypods and half gastro­ age not older than late Tertiary. pods, most of them collected during a reconnaissance INTRODUCTION

survey in 1934, are described and many figured; they 1932. Hoffmeister, J. E., Geology of Eua, Tonga: B. P. Bishop are from beds ranging in age from Miocene to Pleisto­ Mus. Bull. 96, 93 p. cene. Brief discussion of paleoecological conditions (by Records the occurrence of the nautiloid Aturia (p. Ladd and Hoffmeister). 33) in bedded volcanic tuffs believed to be Miocene in 1959. Charig, A. J., in Bartholomew, R. W., Geology of the Lau- age. toka area north-west Viti Levu: Suva, Fiji, Geol. Survey 1935. Ostergaard, J. M., Recent and fossil marine Mollusca of Dept. Bull. 2, 25 p., geol. map. Tongatabu: B. P. Bishop Mus. Bull. 131, 59 p. Sixteen mollusks, 3 pelecypods and 13 gastropods, are A total of 39 fossil mollusks (26 gastropods and 13 identified by A. J. Charig and C. P. Nuttall (p. 18-19) pelecypods) from Tongatabu and Vavau are identified from two localities in bedded tuffaceous sediments with Recent species. Limestones containing fossils be­ mapped as part of the Sambeto series. Twelve fossils are identified with still-living species, three others are com­ lieved to be late Pleistocene in age. pared with such forms. Only one species appears to 1941. Miller, A. K., An Aturia from the Tonga Islands of the represent an extinct species though several are known central Pacific: Jour. Paleontology, v. 15, no. 4, p. to occur as fossils in the Pliocene or later. A Pliocene 429-431. age is thought probable, a late Miocene age possible. Specimen collected by J. E. Hoffmeister from tuffs, 1960. Ibbotson, Peter, Geology of the Suva area, Viti Levu: believed to be Miocene, is described and figured as Suva, Fiji Geol. Survey Dept. Bull. 4, 47 p., geol. map. Aturia cf. A. aturi (Basterot). Detailed report on quarter-degree sheet in south­ eastern Viti Levu that includes many of the late Ter­ COLLECTIONS tiary localities in the Suva Formation that have yielded fossil mollusks. Identifications of Mansfield (1926), Most of the collections on which the present study is Davies (1927, 1930), and Ladd (1934) are listed. based were made by U.S. Geological Survey personnel; 1960. Bartholomew, R. W.. Geology of the Nandi area, western others were loaned for study by museums and other in­ Viti Levu: Suva, Fiji Geol. Survey Dept. Bull. 7, 27 p., stitutions. All important sources are given below: geol. map. Palau. Most of the Palau material was collected by A list of fossils identified by L. R. Cox in 1954 (p. 11) H. S. Ladd in 1958; other collections had been made includes six molluscan generic determinations. earlier by several Geological Survey geologists, par­ 1961. Ibbotson, Peter, Geology of Ovalau, Moturiki and Nain- ticularly in 1948 by a party headed by the late Arnold gani: Suva, Fiji Geol. Survey Dept. Bull. 9, p. 1-7, Mason. geol. map. Mariana Islands. The largest collections of megafos- Quotes in full, Tenison-Woods' brief report of 1897, sils from any of the islands under consideration were pointing out that it is the only report on fossiliferous material from Ovalau. made from Guam by the Pacific Islands Engineers under contract with the U.S. Navy in 1946-50; supplementary 1963. Charig, A. J., The gastropod genus Thatcheria and its re­ collections from Guam were made by a Geological Survey lationships: British Mus. (Nat. History) Bull., Geol. field party under the leadership of J. I. Tracey, Jr., in v. 7, no. 9, p. 257-297. 1951-54 and by H. S. Ladd in 1958. Most of the Saipan Includes description of Thatcheria vitiensis from luffaceous marl of Vanua Levu Formation on Vanua material was collected by a Geological Survey field party Levu; age probably early Pliocene. headed by P. E. Cloud, Jr., in 1948-49, and minor addi­ tions were made by H. S. Ladd in 1958. The few fossil 1963. Rickard, M. J., The geology of the Mbalevuto area: Suva, Fiji Geol. Survey Dept. Bull. 11, 36 p., geol. map. mollusks that have been obtained from Tinian were col­ Includes references (p. 30-33) to mollusks, identified lected by the late Josiah Bridge in 1946 and by Cloud in by H. S. Ladd, from the Singatoka, Suva, and Mba 1949, both of the Geological Survey. series of upper Tertiary area. Marshall Islands. Cores and cuttings were obtained 1965. Ladd, H. S., Tertiary fresh-water fossils from Pacific from drill holes on Eniwetok and Bikini Atolls between islands: Malacologia v. 2, no. 2, p. 189-198. 1947 and 1952. Includes description of a species of Melanoides from Ellice Islands. Cores and cuttings from drill holes beds formed in mangrove swamp on Viti Levu in late obtained by the British on Funafuti Atoll between 1896 Tertiary time. and 1898 (David and others, 1904). Material was bor­ TONGA rowed from the British Museum (Natural History), the 1926. Mansfield. W. C., Fossils from * * * Vavao, Tonga Islands Australian Museum in Sydney, and the Museum of Com­ * * *: Carnegie Inst. Washington Pub. 344, p. 85-104. parative Zoology at Harvard. Three mollusks, one identified with a living species and one related to a living form, are listed, and a post- New Hebrides. Small collections were made by H. T. Tertiary age is suggested. Stearns of the Geological Survey in 1943; some material CHITONS AND GASTROPODS FROM WESTERN PACIFIC ISLANDS

was borrowed from M. R. Abrard of the Museum Na­ History), the Australian Museum, and the Museum of tional d'Histoire Naturelle in Paris. Comparative Zoology at Harvard loaned samples from Fiji. The collections of larger mollusks described by the drill holes on Funafuti. Professor Rene Abrard of the Ladd in 1934 and 1945 have been supplemented by un- Museum National d'Histoire Naturelle loaned fossil described larger mollusks from Viti Levu collected by material described by him from the New Hebrides. Dr. Ladd in 1934 and by micromolluscan material not previ­ C. Beets of Leiden, Netherlands, kindly checked identi­ ously described. Additional material collected in recent fication of a species that appeared to be closely related years has been furnished by the Geological Survey De­ to a form described by him from the Miocene of Borneo. partment in Fiji and by William Briggs of the U.S. Mr. W. M. Briggs, Jr., and Mrs. Evelyn Bourne, both Geological Survey who visited Viti Levu in 1962. of the U.S. Geological Survey, aided in the preparation Tonga. A few Tertiary mollusks were collected by of much of the material, and Mr. Briggs made almost all J. E. Hoffmeister in 1926 and 1928; post-Tertiary mate­ the photographs of fossils. I am indebted to Drs. H. A. rial was collected by J. Ostergaarcl in 1926 and was Rehder and J. P. E. Morrison, of the U.S. National loaned by the Bernice P. Bishop Museum in Honolulu. Museum, and Dr. Robert Robertson, of the Academy of The largest molluscan collections are those from Eni- Natural Sciences, for assistance in the identification of wetok, Guam, and Fiji, in that order. The Eniwetok certain mollusks. The manuscript has benefited from collections from drill holes are rich in well-preserved critical reviews by W. P. Woodring of the U.S. National micromollusks. Those from Guam and Fiji are outcrop Museum and by Dr. R. T. Abbott of the Academy of samples, and many of them are molds or calcite casts; Natural Sciences. they are comparatively poor in micromollusks. GEOLOGY ACKNOWLEDGMENTS STRATIGRAPHY Prior to her retirement in 1952, the late Dr. Julia Detailed studies in recent years have greatly increased Gardner made preliminary determinations of many of our knowledge of the Cenozoic sections in several of the the fossil mollusks collected by Geological Survey per­ island groups under consideration. In the Pacific Basin sonnel in the Mariana Islands and Palau. Her identifi­ proper, a standard section has been established from cations of Saipan mollusks were published in Professional results of deep drilling in the Marshall Islands (described Paper 280-A (Cloud and others, 1956). In connection in the numerous chapters of U.S. Geol. Survey Prof. with her studies, she assembled a useful index of refer­ Paper 260, especially Emery and others, 1954; Cole, ences on island fossil mollusks. In 1947 she visited Palau 1958; Todd and Low, 1960; Ladd and Schlanger, 1960; where she collected from the Palau Limestone in the Schlanger, 1963). Outside the basin, in the Mariana Koror area. Islands (Cloud and others, 1956; Doan and others, 1960; In 1945, I discussed Palauan geology with the late Tracey and others, 1964) ; in Palau, (Mason and others, Prof. Risaburo Tayama in Sendai, Japan, and was given suggestions as to promising places in which to collect 1956) ; and in Fiji, (bulletins published by Geol. Survey fossil mollusks. These suggestions proved invaluable Dept. of Fiji, including: Bartholomew, 1959, 1960; during fieldwork in Palau in 1958. At that time I was Houtz, 1959, 1960, 1963; Ibbotson, 1960, 1962; Rickard, cordially received and was given much assistance by Mr. 1963; Houtz and Phillips 1963; also Cole, 1960); detailed R. P. Owen, staff entomologist with the Trust Territories mapping and paleontological studies have established in Koror. similar sections. In the Ellice Islands, in the New The extensive collections of Recent mollusks at the Hebrides, and in Tonga, available information is much U.S. National Museum contain many shells collected by less complete. Dr. J. P. E. Morrison and others in the Marshall Islands Each of the seven island groups has a section of during Operation Crossroads in 1946-47 and later. These Quaternary limestones and all except Funafuti in the shells were particularly useful in studying fossils ob­ Ellice group are known to have a Tertiary sequence as tained from drill holes. The Academy of Natural Sci­ well. The known Tertiary in all groups, except that in ences in Philadelphia, through Dr. R. T. Abbott, curator, the New Hebrides, extends downward into the Eocene. loaned Recent chitons for comparative studies and gave No Paleocene has been reported from any of the island full access to the collections when I visited Philadelphia groups. in 1964; the Bishop Museum, through Mr. E. H. Bryan, The subdivisions of the Tertiary are based on the sys­ Jr., curator, loaned the fossil material from Tonga col­ tem developed for the East Indies by van der Vlerk and lected by Jens Ostergaarcl; the British Museum (Natural Umbgrove (1927). By using larger , the GEOLOGY

TABLE 1. Distribution of Cenozoic sediments in the island area [ X, present; question mark indicates uncertain identification]

Marshall Islands Mariana Islands Fiji Tonga Indo­ Eniwetok Bikini Ellice Guam Saipan Tinian Palau New Viti Lau nesia1 Hebrides Levu

Recent X X X X X X X X X X X Quaternary Pleistocene X X X X X X X X X X

h Pliocene X X X ? X X X X X Upper Upper g Miocene X X X ? X X X X X Tertiary ? f Lower X X X X X X X Miocene e X X X X X X X X d Oligocene Lower c X? X? X X Tertiary b X X X X X X X Eocene a2 X

1 Some workers (Bemmelen, 1949, p. 88) place part of Tertiary g into the Pliocene with Tertiary h. 2 Occurrence of Tertiary a ba^ed on smaller Foraminifera on Sylvania Guyot adjoining Bikini (Hamilton and Rex, 1959).

Tertiary sequence was subdivided into six units, desig­ Globigerina ooze described by Hamilton and Rex (1959) nated by the letters a-/. Later, two younger stages g from the top of Sylvania Guyot adjacent to Bikini. The and h were added (Leopold and van der Vlerk, 1931; ooze contained no mollusks. table 1, this paper). This classification has proved to be Limestones of late Eocene age (Tertiary b] are widely exceedingly useful in the western Pacific island groups. known in Eniwetok, the Marianas, Palau, Fiji, and In the atoll groups (Marshall and Ellice Islands), the Tonga. Mollusks occur in some of these limestones, but sedimentary rocks consist of reef limestone and dolomit- they are rare, and in many places they are poorly pre­ ized limestone. Similar limestones occur in the high served; none from the families here treated has been island groups along with a variety of terrestrial and specifically identified. In Fiji and Tonga the limestones marine tuffs and coarser volcanic sediments. The have yielded diagnostic larger Foraminifera, but no other Cenozoic sedimentary rocks are known to rest on volcanic identifiable fossils. In Palau, numerous fragments of an rocks in most areas. In the Ellice Islands, no volcanic upper Eocene limestone containing larger Foraminifera, rocks are exposed nor have they been reached by the algae, and unidentifiable mollusks occur in a volcanic drill, but seismic evidence suggests such a foundation at breccia. In the Mariana Islands, upper Eocene rocks have a depth of about 1,800 feet (Gaskell and Swallow, 1953, yielded a considerable variety of fossils, including p. 3). In Fiji (McDougall, 1963) and Tonga (Guest, Foraminifera, radiolarians, discoasters, algae and in 1959, p. 3), plutonic rocks are known; their presence records more complex histories than in other island TABLE 2. Major stratigraphic subdivisions recognized in groups. The Tongan plutonic rocks are thought to be of holex drilled in the Marshall Islands pre-Tertiary age. Fossils from the section established by deep drilling Eniwetok Bikini in the Marshall Islands have been studied by several Stratigraphic divisions Depth Depth workers; their findings have been published as chapters (feet) (feet) of U.S. Geological Survey Professional Paper 260. The major divisions recognized are shown in table 2. With Post- Miocene 0-615 0-700 slight modification, this is the arrangement given by Cole Upper Miocene Tertiary g 615-860 700-980 (1958, p. 745). Tertiary / 860-1,080 980-1,166 Lower Miocene EOCENE Tertiary e 1,080-2,780 1,166-2,556 + The only known occurrence of lower Eocene (Tertiary Upper Eocene Tertiary b 2,780-4,610 a) sediments in the island area is the phosphatized 8 CHITONS AND GASTROPODS FROM WESTERN PACIFIC ISLANDS

some places fragmentary and poorly preserved mollusks exceed 2,000 feet (table 2). All three major subdivisions have been found. In the Marshall Islands, some Eocene of the Miocene (Tertiary e, /, and g ) are represented, but mollusks have been recovered from deep holes on Eni- the section is not complete, inasmuch as a solution uncon­ wetok. These include poorly preserved bivalves {Area formity appears at the top of Tertiary e (Schlanger, 1963, and Pecten), but most are the molds of minute gastro­ p. 995). Miocene reef limestones are also found in Palau. pods, including turbinids and eyclostrematids, that are The total section exceeds 750 feet, but some parts may not identifiable. be younger than Miocene (Cole, 1950; Mason and others, 1956, p. 55-59). In at least two areas in Palau the OLIGOCENE Miocene includes thin tuffaceous limestone and marl Limestones containing larger Foraminifera diagnostic that are here assigned to the upper Miocene (Tertiary g). of the lower Oligocene of the Indonesian section (Tertiary On Saipan and Tinian in the Mariana Islands, the lower c) have been found in Fiji and in Guam (Cole 1960, Miocene (Tertiary e) limestones are 750 to nearly 1,000 1963). The beds containing these fossils are restricted in feet in maximum thickness and include some tuffaceous their distribution and to date (1965) have yielded no facies (Cloud and others, 1956, p. 62-77; Doan and identifiable mollusks. Some of the limestones on Guam others, 1960, p. 60-62). Tertiary e rocks on Guam exceed that contained Oligocene larger Foraminifera also yielded 2,000 feet, but most of the sequence consists of volcanic an assemblage of smaller Foraminifera that is definitely flows and breccias. Although some of the included lime­ early Oligocene (Tertiary c) in age (Ruth Todd, oral stones are of shallow-water origin, Globigerina-rich sedi­ commun., 1963). ments, of deeper water origin, are present. On Guam the The section drilled in the Marshall Islands includes Tertiary e rocks are overlain by several hundred feet of beds containing smaller Foraminifera that may repre­ younger limestones; some of these are definitely of Ter­ sent the lower Oligocene (Tertiary c) but the corre­ tiary / age, others may be Tertiary g. (Tracey and others, lation is questionable (Todd and Low, 1960). In drill 1964). In Fiji the Miocene sequence is dominantly vol­ holes F-l and E-l on Eniwetok, there is an interval of canic. It consists of many thousands of feet of agglomer­ about 100 feet (2,687-2,780 ft) that Cole (1958, p. 745, ates, tuffs, and marls, some water laid, together with a 748) labeled "unknown" because it yielded no diagnostic variety of igneous rocks. Limestones of shallow-water larger Foraminifera. Above this interval the beds con­ origin are at least 200 feet thick in some areas. Miocene tain lower Miocene Foraminifera (Tertiary e ) and below rocks of comparable types have been reported from the they contain upper Eocene species (Tertiary 6). Along less well known New Hebrides (Mawson, 1905; Abrard, with the smaller Foraminifera that are suggestive of the 1946). In Tonga the known Miocene is thin; it consists lower Oligocene, the questionable beds yielded three of a series of volcanic tuffs totaling 200-300 feet in thick­ specimens of Rissoina ailinana Ladd, n. sp., a species ness (Hoffmeister, 1932, p. 30, 33). that occurs in some Tertiary e samples in both Eniwetok and Bikini. Also recovered were nine specimens (from POST-MIOCENE four samples) of a well-preserved Miocene Ampullina, In the island area it is difficult, if not impossible, to described from East Borneo by Beets (1941) as Globu- recognize age boundaries in the post-Miocene sediments. laria berauensis.^ Because of the occurrence of these Diagnostic larger Foraminifera which are so useful in mollusks, I have tentatively assigned the unknown inter­ subdividing the Miocene and older Tertiary beds have val to the Miocene. not been found. Other organisms, especially planktonic No beds that would represent the upper Oligocene smaller Foraminifera, discoasters, and radiolarians, offer (Tertiary d) have been found in any of the island groups great promise, but these organisms are not everywhere here considered. The Fina-sisu Formation of Saipan, present, and their geologic distribution in the islands has previously assigned to the late Oligocene (Todd and not yet been adequately determined. Mollusks, even others, 1954) on the basis of smaller Foraminifera, is now where well preserved and abundant, are of limited use­ regarded as early Miocene in age (Ruth Todd, oral fulness in determining exact post-Miocene ages. commun., 1963). In the Marshall Island drill holes, the top of the

MIOCENE Miocene has been agreed upon by those who have studied the Foraminifera from cores and cuttings. The post- Miocene sedimentary rocks have been recognized in all Miocene section ranges from 510 to 700 feet in thickness, the island groups except in the Ellice Islands. In the Eniwetok drill holes, shallow-water lagoonal limestones but it has not been subdivided accurately (Cole 1958, p. 745; Todd and Low, 1960, p. 802, 807). These limestone 1 Mr. Beets kindly checked the identification of this species by comparing an Eniwetok shell with his type in the museum in Leiden. beds thought to be mostly lagoonal, have not yielded PALEONTOLOGY 9

assemblages of diseoasters or radiolarians. The smaller In eastern Fiji (Lau), the Fulanga Limestone is com­ Foraminifera in the elevated post-Miocene reef lime­ posed of elevated veneers of reef limestone, occurs on stones of Fiji, Tonga, and Palau, are preserved mostly as two or three islands, and has been referred tentatively unidentifiable molds, as are those in most of the Quater­ to the Pleistocene. Paleontologically it yielded two pre­ nary sediments drilled on Funafuti. The post-Tertiary viously undescribed echinoids, a new decapod , limestone of the Mariana Islands contains both larger and a few species of still-living mollusks. Among the and smaller Foraminifera, but no extinct species are in­ mollusks are species that no longer live in Fiji. The pre­ cluded and hence no exact stratigraphic boundaries are ceding data suggest an appreciable age for the Fulanga, indicated. Some of the elevated limestones of the New but they do not clearly indicate Pleistocene. That inter­ Hebrides contain molluscan species previously reported pretation was based almost entirely on field evidence from the Pliocene of Java (Abrard and La Rile, 1937). (Ladd and others, 1945, p. 267, 313, 322, 380).

PLIOCENE CORRELATION The Pliocene-Pleistocene boundary is perhaps the most Age determinations and correlations involving major difficult Cenozoic boundary to recognize in the island stratigraphic units in the several island groups are based area. Environmental conditions in the tropical islands on the letter classification established for Indonesia (van seem to have been little affected by the onset of glaciation tier Vlerk and Umbgrove, 1927; Leopold and van der in other parts of the world, and no clear stratigraphic Vlerk, 1931 L No attempt is made to tie these Indonesian break appears. units to the stages of the standard European sequences. In cores of deep-sea sediments containing layers of ice- Efforts of this sort have been made, but most such efforts rafted materials, the earliest of these can be taken as the have been regarded as tentative, even by their proposers base of the Pleistocene, and correlations with other deep- (Glaessner, 1943, 1959; Todd and others, 1954; Cloud, sea sections can be made on the basis of wide-ranging 1956; Eames and others, 1962). The exact ages (by the Foraminifera or other planktonic organisms. Eventually Indonesian letter system) of some of the Tertiary units a system of this sort may be successfully applied to some in the islands are in question because of conflicting inter­ of the sediments of the island area. pretations of faunal evidence, notably that of the larger versus the smaller Foraminifera. These differences are PLEISTOCENE AND RECENT still being discussed vigorously. (Cole and others, 1960; In the absence of definitive paleontologic evidence, it Glaessner, 1960; Eames and others, 1962). The mollusks, is not possible to recognize Pleistocene beds with cer­ which rarely occur in beds with diagnostic Foraminifera, tainty, though suggestive physiographic evidence has are not deeply involved with questions of exact correla­ been called upon in several areas. In the Bikini drill tion. The correlations shown in table 3 are based more holes, three rock units above 294 feet, characterized by heavily on evidence from the larger Foraminifera than distinctive species of still-living smaller Foraminifera, on that of other groups of fossils. It is recognized, how­ seem to be related to present physiographic features. ever, that eventually the evidence of such mobile plank- These rock units are thought to represent three late tonic groups as some of the smaller Foraminifera, the stages of reef growth, probably separated by two periods Radiolaria (Riedel, 19591, and especially the diseoasters of emergence representing Pleistocene shifts in sea level (Bramlettc and Riedel, 19541 may offer modified, and (Emery and others, 1954, p. 2, 75, 132-133). perhaps sounder, correlations. Boundaries and units that On Saipan, the name Mariana was applied to lime­ are questionable are so marked in table 3, and it should, stones now as much as 500 feet above existing sea level perhaps, be repeated that the exact ages of all post- and the name Tanapag to limestones below 100 feet. The Miocene units in the island area are debatable. Mariana includes reef and lagoonal deposits, whereas the Tanapag represents rock of an elevated fringing reef. PALEONTOLOGY The Mariana was assigned an early, and the Tanapag a GEOGRAPHIC AND GEOLOGIC DISTRIBUTION younger, Pleistocene age. These interpretations are sup­ OF SPECIES ported by a period of faulting that intervened between The geographic distribution of all the species treated the benching of the Mariana and the deposition of the is shown in table 4. The Marshall Island faunas are the Tanapag. Carbon-14 analyses of the Tanapag seem to richest, and more than half of the total number of named support the postulated younger Pleistocene age (Cloud forms are recorded from Eniwetok alone. Fiji ranks and others, 1956, p. 2, 79-80, 87). On Guam, the Mariana in number, Palau a poor third. Faunas from the Limestone yielded no diagnostic larger Foraminifera but other island groups are smaller but none of these areas, was assigned a Pleistocene, or possibly Recent, age (Cole, except the Mariana Islands, has been adequately col­ 1963, p. El, E10). lected. H m r- QUATERNARY s^ SYSTEM d T3 > m > m 33 33

O m 8 8 33 m (0 f O 3 D o S 3 O (C 3 3 3 Lower Upper Lower Upper Lower Upper

LETTER « o- - a. *-*, «S =» CLASSIFICATION

33 ENIWETO Reef complex, chiefly O __. 3 lagoonal and forereef MARSHALL

Globigenna CD Reef limestone, ooze1 - . "O chiefly bed 2

2-S ^ H^ S FUNAFUTI limestone r-m o Reef O m O

-r r- ??Babelthuap Formation' Formation Ngeremlengui 3 depositsBeach = ___Peleliu ^- f. 1 I 1 PALAU c 8 K * 6 " 3 3 m (0 0 "u

s W2, ". r- .^1 " Pyroclastic Limestone Tagpochan graveland Raisedbeach TINIAN MARIANA rocks (D -< as- I O 3 3 U O to' to ^ *

3 > CD "~ CD W ^ GUAM 1 0 5^ i " f | ft O)' CL o S (0 5-3 if O 3 O 0 3 01 O 3 3

limestone1 3 c | limestone HEBRIDES 33 NEW Reef

s H limesto SeTavua Alluvium Seriesa limesand Plutoni oo ¥ SerVatia Wainima cr c lateritt H Tholo o 00 = (0 g m o u> m o_ *' (n 3 c 3 Q. -n

o r 2 3 a 3? °- of Ul If 1% 3 3 O 013 c ° 0

013

H <- ^33 nestone 3 "O "° (n (D Reef o Z, 3 3 (0

omovd WOUA saodOHiSvo QKV SKOXIHO OT PALEONTOLOGY 11

The geologic distribution of species is shown in table section of cavernous Palau Limestone. Around the penin­ 5. The numbers of named species from each of two stages sula today there is a broad platform bordered by of the Miocene (Tertiary / and g I exceed those recorded mangrove swamps. This flat is nearly awash at low tide from all other divisions of the Cenozoic. and is partly covered by waving grass. Shore-flat mollusks are abundant. Apparently, conditions were PALEOECOLOGY similar during the late Miocene. Many bedding planes Many of the Cenozoic sediments that out on the in the marls are crossed by carbonaceous stripes, thought islands, or have been reached by the drill below sea level, to represent eel grass, and the same genera of shallow- are limestones that were formed in shallow7 water on water mollusks are common, though the species are dif­ reefs or in adjacent lagoons. Such sediments dominate ferent. All but 2 of the 18 Palauan mollusks described in the sections drilled below the three atolls Eniwetok, in the present report were obtained from the marl on the Bikini, and Funafuti. Similar reef limestones crop out Goikul . extensively in the Mariana Islands, in Palau, and in In the Mariana Islands, particularly on Saipan and eastern Fiji. At Eniwetok and in the Mariana Islands, Guam, Cenozoic reef-associated limestones and certain the shallow-water limestones occur with off-reef lime­ Globigerina-Y\ch sediments that suggest deeper waters stones that appear to have been accumulated in somewhat have been mapped and studied in detail. Paleoecological deeper water, the indicated depths being not less than interpretations, based in large part on the distribution 100 fathoms (Todd, 1957, p. 271; Todd and Low 1960, of Foraminifera, have been offered (Todd and others, p. 812-815; Schlanger 1963, p. 999-1002). Among the 1954, p. 677; Cloud and others, 1956, p. 68, 80-81, 86-88; high islands, particularly in Fiji and the New Hebrides, Hanzawa, 1957, p. 33-34; Todd, 1957, p. 265, 273-283; are thick sequences of tuffs and marls, many of which Cole, 1963, p. E11-E12). were deposited in marine water. Globigerina-rich beds in Mollusks left a meager fossil record on Saipan, par­ these sections point to water of at least moderate depths, ticularly as to the kinds considered in the present report. but lenticular of shallow-water limestones are Mollusk collections from Guam are larger and more included between them. Such associations raise many varied, but most of those here described are types com­ problems that have not, as yet, been satisfactorily solved. monly found near the reef edge or on the reef flat. Col­ On most islands, both lateral and vertical changes in lecting localities on Guam are concentrated in the waist facies are abrupt and even repetitious. Paleoecological of the island where the several facies of the Mariana interpretations of a given fossiliferous bed can be made Limestone are widely exposed. This same area is notably without great difficulty but the environmental history poor in Foraminifera, because many of these organisms recorded by sequence of appreciable thickness is much lived in moderate to fairly deep water. more complicated. The limestone sections drilled beneath Eniwetok and Mollusks occur in most of the kinds of rocks mentioned Bikini in the Marshall Islands are all reef associated. above but the species described in the present report were Many of the highly fossiliferous beds, especially those all derived from shallow-water deposits that formed on rich in mollusks, appear to have been deposited in reefs, reef flats, shore platforms, and in lagoons adjacent lagoons, but other environments reef wall, open , to reefs. This report deals with the scanty record left and off-reef deposits are also found. Paleoecological by the chitons,- and the fuller records of 15 families of interpretations have been summarized and graphically gastropods. Taken together, the fossils represent only portrayed by Scblanger (1963, p. 998-1001). about one-sixth of the collections available, and hence Of particular interest is a thick zone that roughly en­ full paleoecological interpretations are not attempted at compasses the beds assigned to Tertiary g and /. This this time. zone was found in all the deep holes drilled on Eniwetok In Palau, the thick sections of cavernous rock that and Bikini. The section, referred to by Schlanger (1963, form the Palau Limestone of southern Babelthuap and 1). 10001 as the "Coral-mollusk-rich zone," apparently the numerous islands that lie to the south are of reef never was raised above the sea to be leached and re- origin. Mollusks are abundant in the Palau, but most of crystallized. Its fossils are almost perfectly preserved, them are unidentifiable molds of common reef types, many mollusk shells even retaining traces o,f their original including trochids and turbinids. Locally, however, at color patterns. The beds are unconsolidated and core the base of the Palau, tuffaceous and marly beds carry recovery was difficult, but rich concentrations of mollusks a rich molluscan fauna of late Miocene (Tertiary g) age. were obtained in some core runs. The cored material On the Goikul Peninsula of southeast Babelthuap, a thin appeared to be far richer in mollusk shells than any sedi­ wedge of marl lies between the Airai Lignite and a thick ments dredged from the floors of the existing lagoons. 12 CHITONS AND GASTROPODS FROM WESTERN PACIFIC ISLANDS

TABLE 4. Geographic distribution of species

Species Palau Guam Saipin Eniwetok Bikini Funafuti New- Fiji Tonga and Tinian Hebrides

Sohizochitonidae : Schizochiton incistts yoikulensis Ladd. n. subsp v marshallensis Ladd, n. sp v Lor ic ella sp. A Chitonidae : Lucilina russelli Ladd, n. sp sp. A______v sp. B.