a 2 7 of Canada Ottawa 1974 Publications in Biological National Museums Oceanography, No. 7 National Museum of Natural Sciences Molluscs from Baffin Bay and the Northern North Atlantic Ocean Arthur H. Clarke Publications d’Océanographie biologique, n° 7 Musées nationaux du Canada FESS ILEUS Re He oare Sear ye ~ CALIFORNIA . Speen oak DE AY | ACADEMY OF SCicIN( , bct - 9 1974 } LIBRARY a Seen nce OT Musée national des Sciences naturelles Molluscs from Baffin Bay and the Northern North Atlantic Ocean National Museum of Natural Sciences Publications in Biological Oceanography, No. 7 Published by the National Museums of Canada Staff editor Bonnie Livingstone Musée national des Sciences naturelles Publications d’Océanographie biologique, n° 7 Publié par les Musées nationaux du Canada Molluscs from Baffin Bay and the Northern North Atlantic Ocean Arthur H. Clarke ©Crown copyrights reserved National Museum of Natural Sciences National Museums of Canada Ottawa, Canada Third quarter 1974 Catalogue No. NM95-7/7 Available by mail from the National Museums of Canada Marketing Services Ottawa, Ontario K1A OM8 P0987654321 Y7987654 Printed in Canada ©Droits réservés au nom de la Couronne Musée national des Sciences naturelles Musées nationaux du Canada Ottawa, Canada Troisiéme trimestre 1974 No de catalogue NM95-7/7 L’éditeur remplit les commandes postales adressées aux Musées nationaux du Canada Service de distribution Ottawa, Ontario K1A OM8 T0987654321 A7987654 Imprimé au Canada Contents List of Figures, vi List of Tables, vii Résumé, viii Summary, ix Biographical Note, x Acknowledgements, xi Introduction, 1 | Materials and Methods, 1 Taxonomy, 13 Lepidopleuridae, 13 Patellidae, 13 Trochidae, 13 Trichotropidae, 13 Naticidae, 14 Pyramidellidae, 14 Malletiidae, 16 Limidae, 16 Verticordiidae, 18 Range Extensions, 19 Zoogeography, 21 Discussion, 22 References Cited, 23 vi List of Figures 4 Stenosemus albus (L), Sta. 16, 13 2-4 Torellia vestita Jeffreys, Sta. 775, 13, 14 5 Melanella orphanensis (n. sp.), holotype, Sta. 6, 15 6 Pyramidella sp., Sta. 6, 15 7,8 Tindaria sp., Sta. 23, 16 9 Limatula louiseae (n. sp.), holotype, Sta. 9, 17 10, 11 Lyonsiella sp., Sta. 1039, 18 List of Maps 1 Research area, showing dredging stations, xii List of Tables. 1 Basic station data, 2 2 Sediment data, 4 3 Mollusc species and stations, observed depths, and observed regional distributions, 5 4 Species representation of geographic faunal groups of marine prosobranchs and lamellibranchs, 21 Vii viii Résumé En 1961, 1970 et 1971, ona fait 48 péches, principalement dans des milieux archibenthiques et abyssaux de la baie de Baffin et de Atlantique nord entre Terre-Neuve et I’lslande. Les prises comp- tent 174 especes de mollusques dont plusieurs sont nouvelles et certaines autres rarement collectionnées. L’analyse des spécimens réevele des extensions de répartitions importantes et certaines caractéristiques des populations: 1 on observe entre le Groenland et I’lslande une frontiére fauni- que euro-americaine septentrionale; 2 les faunes archibenthiques et abyssales de la baie de Baffin se différencient de celles de la mer du Labrador de maniére a s’accorder avec |l’age géenéralement attribué a la baie de Baffin; 3 la zoogéographie des mollusques abyssaux et archibenthiques de |’Atlantique nord parait dynamique et non pas statique. L’auteur expose la taxonomie et la zoogéographie de plusieurs espeéces. ll en décrit deux considérées nouvelles, la Melane/la orphanen- sis et la Limatula louiseae. Summary Forty-eight hauls, principally from archibenthal and abyssal depths, were taken in Baffin Bay and in the North Atlantic between Newfoundland and Iceland in 1961, 1970 and 1971. The collections contain 174 species of molluscs, including several that represent new species, rarely collected species, or substantial range extensions. Analysis of the material indicates that: 1 a North American—European faunal boundary exists between Greenland and Iceland; 2 the archibenthal and abyssal fauna of Baffin Bay have differen- tiated from the Labrador Sea fauna to an extent that is in agree- ment with the presumed age of Baffin Bay; and 3 the zoogeography of North Atlantic archibenthal and abyssal molluscs appears to be dynamic and not static. The taxonomy and zoogeography of several species is discussed. Melanella orphanensis and Limatula louiseae are described as new. Biographical Note Arthur H. Clarke, Head of the Invertebrate Zoology Section and Curator of Molluscs at the National Museum of Natural Sciences, National Museums of Canada, was born in 1926 in Danvers, Massachusetts. He received his M.Sc. from Cornell University in 1958 for work on freshwater molluscs and his Ph.D. from Harvard University in 1960 for research on deep-sea marine molluscs. From 1957 to 1959, Dr. Clarke worked as a marine biologist for Columbia University, and in 1959 he joined the staff of the National Museums of Canada. He has published approximately 80 scientific papers, dealing principally with the taxonomy, distribution, and ecology of North American marine and freshwater molluscs. Dr. Clarke is past-president (1968-69) of the American Malacol- ogical Union and is currently editor of AMU publications. He is also associate editor of the scientific journals Malacologia and The Nautilus. In 1971 he was appointed Adjunct Professor of Biology at Carleton University. His current projects include research on the molluscs of Canada and training Canadian students in malacology and related fields. Acknowledgements The author is grateful to the Bedford Institute of Oceanography, Dartmouth, Nova Scotia, for ship time and use of facilities aboard C.S.S. Dawson and C.S.S. Hudson, to the United States Naval Oceanographic Office, Washington, D.C., for similar support aboard U.S.S. Lynch, and to the Museum of Natural History, Smithsonian Institution, for access to their complete and well-managed collec- tion of molluscs. Mr. G. Leonard Johnson, Chief Scientist on board U.S.S. Lynch, and to the Museum of Natural History, Smithsonian material for this study. | also thank Mr. Brian T. Kidd for excellent and extensive assistance in the field; Mrs. Muriel F. |. Smith, Mrs. Jane Topping and Miss Patricia Solowan for dedicated assistance in the laboratory; and Mr. Stanley W. Gorham for collection of material off the Grand Banks. Outstanding artistic support was provided by Miss Aleta Karstad, who prepared the fine specimen drawings, and Mr. Charles Douglas, who prepared the map. Discussions with colleagues, particularly Dr. Robert C. Bullock, Dr. Edward L. Bousfield, Dr. Roy D. Hyndman, Dr. Charlotte E. Keen, Dr. Michael Rex and Dr. David |. Ross, were also useful. Any errors, of course, are mine alone. 4] Introduction Several opportunities have arisen during the past few years to carry out archibenthal and abyssal dredging in Baffin Bay and the northwestern North Atlantic Ocean. The prin- cipal area of interest was the deep basin of Baffin Bay, a region that contains a poorly known and partly endemic fauna. It was hoped that further study of the fauna might contribute not only to a fuller understanding of its composition and probable origin, but also provide information of significance to the history of plate tectonics in the region. Of course, comparative data from adjacent regions were necessary, and therefore dredgings were carried out in the Labrador and Greenland seas; previously collected material was also studied. The molluscan fauna collected is of un- usual interest. A total of 174 species was found, and several represent new species, rarely collected species, or substantial range extensions. Analysis of the results shows that the species occurrences may contribute not only to the history of geological events in Baffin Bay, but also to a fuller understanding of the boundaries of major zoogeographic regions in the northern North Atlantic Ocean. The discovery of some well-known species far beyond their previously known geo- graphic limits also provides evidence that geographical distributions of some archi- benthal molluscs may change significantly in a few decades. This casts doubt on the present accuracy of composite distribution patterns deduced from museum collections that have been assembled throughout the past 100 years. These questions and others are consid- ered in some detail in the following sections. A preliminary discussion has also been published recently (Clarke 1973). Map 1 Research area, showing dredging stations. @ C.S.S. Dawson and C.S.S. Hudson stations A U.S.S. Lynch stations a A. T. Cameron station Materials and Methods Most of the specimens were collected during three separate cruises in 1970 and 1971. From 7 to 22 September 1970, Mr. Brian Kidd and | travelled in Baffin Bay on board C.S.S. Dawson, an oceanographic ship operated by the Bedford Institute of Oceanography, Dart- mouth, Nova Scotia. Seven dredge hauls were taken using a modified Menzies Dredge. Between 23 May and 4 June 1971, Mr. Kidd was on board U.S.S. Lynch between Argen- tia, Newfoundland, and Reykjavik, Iceland. The U.S.S. Lynch is an oceanographic vessel operated by the United States Naval Ocean- ographic Office, Washington, D.C. Nine dredge hauls were made using an Arctic Dredge (Clarke 1972), or a standard rock dredge modified by insertion of a wire-mesh screen liner. After the Lynch left Iceland to return to Newfoundland, dredging was con- tinued by Scientist-in-Charge G. Leonard Johnson. The modified rock dredge was used, and an additional 26 dredge hauls were made. From 17 September to 10 October 1971, | carried out another series of dredgings in Baffin Bay, this time aboard the Bedford Institute’s famous oceanographic vessel C.S.S. Hudson. The Arctic Dredge was used, and twelve archibenthal and abyssal dredge hauls were taken with it. Five shallow dredge hauls were also made near Thule and Godt- haab, Greenland, using a modified Agassiz Dredge, and shore collecting was also done at Thule. | also studied material collected on pre- vious expeditions. One dredge haul in 775 fathoms near the Grand Banks of Newfound- land is of special interest. That haul was made by Mr. Stanley W. Gorham in 1961 from the A.T. Cameron, a Fisheries Research Board of Canada vessel, using a modified Agassiz Dredge. The original station number (15%) has been changed to 775 in the table station data and elsewhere. Specimens col- lected by Dr. Howard Hume of Dalhousie University, Nova Scotia, during core sam- pling for sediment studies in Baffin Bay were also useful. These collections and others are referred to in the text. Station data are summarized in Tables 1 and 2, and the mollusc species collected are listed in Table 3. Materials and Methods Table 1 Basic station data Sta. No. 775 Lat. N. 5) Ops Papks Serta. 51°06:6’ 63°04.7’ 63°06.7’ 64°37.7’ 64°27.8’ 63°38.6’ 63°17.6’ 63°56.8’ 62°30.5’ 61°36.6’ 61°22.6’ 59 57-8" 60°03.7’ 60°04.6’ 60°04.8’ 60°01 .9’ 60°07.1’ 60°08.6’ 60°04.6’ 90 30.0 oe 20 45°30’ 73°19.4’ 73-00.7’ 73° 13.4’ 73°30.24’ T3295 COTS 66°10.5’ 76°34’ 76°34’ 76°34’ 76°34’ 76°34’ 76°00.8’ Tf Ver’ To 90.0 74°06.4’ 73° 25.8’ 74°13’ 7215’ 71°56.8’ Long. W. 46°22.0’ oo 09.0 37°47.3’ 24°02.8’ 24°00.0’ 23°58.3’ 24°23.1/ 23°24.4’ 24°13.5’ 26°51.4’ 2f 22.0 23-20,1 28°43.9’ 46°35.4’ 46°49.5’ 46°50.6’ 46°44.0’ 46°41.1’ 47°01.7’ 47°06.5’ 47°10.5’ 42°54.2’ 51°42.2’ 48°17’ 13, 02.5’ 74°34.’ Gf St.d 65°33.24’ 64°33.9’ Sr oT es 57°33.6’ 68°50’ 68°50’ 68°50’ 68°50’ 68°50’ tt to 75°31.4’ 74°17.4’ T1278 66°55.3’ 62°09’ 63°47’ 62°46.8’ Depth (fm) Region (uncorrected) U.S.S. Lynch, 1971 Labrador Sea 958 Labrador Sea 2354 Labrador Sea 1918 Iceland Shelf 240 Iceland Shelf 220 Iceland Shelf 58 Iceland Shelf 86 Iceland Shelf oF Iceland Shelf 55 Iceland Shelf 320 Greenland Sea 650 Greenland Sea 600-700 Greenland Sea 620-740 Greenland Shelf 260-320 Greenland Shelf 800-950 Greenland Shelf 660-700 Greenland Shelf 550-650 Greenland Shelf 380-460 Greenland Shelf 405-490 Greenland Shelf 220-400 Greenland Shelf 480-650 Labrador Sea 1810 Labrador Sea 215 A.T. Cameron, 1961 off Grand Banks 775 C.S.S. Dawson, 1970 Baffin Bay 509 Baffin Bay 489 Baffin Bay 1220 Baffin Bay 1268 Baffin Bay 1027 Baffin Bay 447 Davis Strait 314 C.S.S. Hudson, 1971 Thule beach Thule 92 Thule 25 Thule 85-115 Thule 95-110 Baffin Bay 260 Baffin Bay 312 Baffin Bay 208 Baffin Bay 600 Baffin Bay 1280 Baffin Bay 360 Baffin Bay 1237 Baffin Bay 1202 Gear DAVIDOV I AI VV SS SS op) 3552255 PPrrrrrrrnnnn Date May May May June June June June June June June June June June June June June June June June June June June June Sept. Sept. Sept. Sept. Sept. Sept. Sept. Sept. Sept. Sept. Sept. Sept. Sept. Sept. Sept. Sept. Sept. Sept. Sept. Sept. Oct. 17 Materials and Methods Sta. Depth (fm) No. Lat. N. Long. W. Region (uncorrected) Gear! Date 1065 72°08.8’ 61°38.0’ Baffin Bay 1000 A oS. 1066 70°31.0’ 63° 16.3’ Baffin Bay 1150 A Oct. 2 to to 70°31.4’ 63°17.3" 1067 68°28.3’ 61°59.6’ Baffin Bay 975 A Oct. 4 to to 68°29.1’ 62°02.8’ 1068 65°46.5’ Sf°52.¢ Davis Strait 295 A Ot.” F 1069 64°10’ 51°43.3’ Godthaab 30 S Oct. 10 1. A Arctic Dredge R_ rock dredge M Menzies Dredge S small biological dredge (Agassiz Dredge) Materials and Methods Table 2 Sediment data Particle size distribution: per cent within size classes (mm) ae particle 1.0- 0.5—- 0.25- 0.12— 0.063- 0.032— 0.016- 0.008- 0.004- <.002 | size 0.12 0.063 0.032 0.016 0.008 0.004 0.002 classes silt, clay silt, clay silt, clay silt, sand Clay, silt Clay, silt Clay, silt sand Clay, silt silt, sand silt, clay Clay, silt Clay, silt Clay, silt Clay, silt Clay, silt Clay, silt Clay, silt silt, clay Materials and Methods Table 3 Mollusc species and stations, observed depths, and observed regional distributions’ Species Polyplacophora Lepidopleuridae 1. Lepidopleurus alveolus (M. Sars) 2. Lepidopleurus asellus (Spengler) 3. Stenosemus albus (L) 4. Hanleya hanleyi (Bean) Aplacophora 5. Proneomenia sp. 6. Chaetoderma cf. nitidulum Lovén 7. Chaetoderma sp. Gastropoda Fissurellidae 8. Emarginula fissura (L) 9. Puncturella noachina (L) Patellidae 10. Lepeta caeca (Miller) 11. Pilidium fulvum (Miller) Trochidae 12. Margarites costalis (Gould) 13. Margarites groenlandicus (Gmelin) 14. Margarites olivaceus (Brown) 15. Margarites umbilicalis (Brod. & Sby.) 16. Margarites vahli (M@ller) 17. Lischkeia ottoi (Philippi) 18. Solariella obscura (Couthouy) 19. Solariella varicosa (Migh. & Ad.) 20. Calliostoma occidentale (Migh. & Ad.) Seguenziidae 21. Seguenzia reticulata (Philippi) Rissoidae 22. Cingula arenaria (Migh. & Ad.) 23. Alvania janmayeni (Friele) 24. Alvania scrobiculata (Muller) 25. Cithna tenella (Jeffreys) Stations 6 14 16 14, 29, 36 1034 1033, 1034 1033, 1058 (17) (6), (14), (23), (32), (35), (37), (1039), 1069 1054, (1058), (1069) (32) 1054 1069 1054 1054 (35), (37), 1033, 1034, 1039 775 (37) 40 36 (23) 1039 1033, 1034, 1039 (1039), (1058) 7 Minimum Depth-range 220-(260) 489 489-509 312-509 (37) 30-(220)— (958) 25-(30)- (312) (550) 314-509 775 (480) 215 220 (600) 314 314-509 (312)-(314) 2354 Off Grand Banks Labrador Sea (t) Off S. Greenland (t) Baffin Bay (t) Off S. W. Iceland —+—+—+ | on Materials and Methods Species Cerithiopsidae 26. Cerithiopsis costulata (Mller) 27. Cerithiella metula (Lovén) 28. Laeocochlis granosa (Wood) Aporrhaidae 29. Aporrhais occidentalis (Beck) 30. Aporrhais serresiana (Michaud) Trichotropidae 31. Torellia vestita Jeffreys 32. Trichotropis borealis Brod. & Sby. Naticidae 33. Amauropsis islandica (Gmelin) 34. Polinices pallida (Brod. & Sby.) 35. Natica clausa Brod. & Sby. Epitoniidae 36. Acirsa costulata (Migh. & Ad.) 37. Epitonium obtusicostatum (G. O. Sars) Aclididae 38. Aclis walleri Jeffreys Eulimidae 39. Eulima stenostoma Jeffreys Muricidae 40. Boreotrophon clathratus (L) 41. Boreotrophon fabricii (Beck) 42. Boreotrophon truncatus (Str@m) Columbellidae 43. Pyrene costulata (Cantraine) Buccinidae 44. Beringius ossiani (Friele) 45. Volutopsius norvegicus (Gmelin) 46. Colus glaber (Verkruzen) 47. Colus fusiformis (Thorson) 48. Colus krampi (Thorson) Stations (1039) 6, (13), (14), (32), 1039 (29), (35), (775), 1039, (1068) (1039) (14) 775 (14), (1039) 16 (14) (13), (14), 15, (21), (30), (35), (775), 1058, 1059, 1062 (6), (13) (23), (32), (33), (35) (26) (13), (14) (13), (327), (37?) (147), (1039), (1069) (13), (147?) (23) (32) (21), (23), (29) (21) 16 1036, 1039, 1061, 1065 Minimum Depth-range =) (314) 314-958 (295)-314— (775) (314) (220) 775 (220)-(314) 86 (220) 58-360- (800) (240)-(958) (460)-(600) (620) (220)-(240) (240)-(4807) (30)-(314) (220?)—(240) (600) (550) (320)-(600) (320) 86 314-1280 Off Grand Banks Labrador Sea (t) Off S. Greenland Baffin Bay es Ge Off S. W. Iceland Materials and Methods Species 49. Colus latericeus (Moller) 50. Colus tortuosus (Reeve) 51. Colus turgidulus minor (Thorson) 52. Colus ventricosus (Gray) 53. Plicifusus kroyeri (Moller) 54. Neptunea despecta (L) 55. Neptunea satura (Martyn) 56. Buccinum cyaneum Bruguiére 57. Buccinum eilatior Tryon Stations (32), (775) 1058, (1064), (1065) 14), (22), (29), (31), (35) (1054) (= B. tenue Gray, preocc.; see Baily 1961) 58. Buccinum finmarkianum Verkruzen 59. Buccinum hydrophanum Hancock 60. Buccinum sericatum Hancock Nassariidae 61. Nassarius incrassatus (Strom) Cancellariidae 62. Admete couthouyi (Jay) Turridae 63. Spirotropis carinata (Philippi) 64. Oenopota cinerea (Moller) 65. Oenopota declivis (Lovén) 66. Oenopota cf. decussata (Couthouy) 67. Oenopota cf. incisula (Verrill) 68. Oenopota nobilis (Moller) 69. Oenopota cf. pyramidalis (Strom) 70. Oenopota reticulata (Brown) 71. Typhlomangelia nivalis (Lovén) Pyramidellidae 72. Eulimella compactilis Jeffreys 73. Melanella orphanensis (n. sp.) 74. Pyramidella sp. Scaphandridae 75. Cylichna alba (Brown) 76. Cylichna cylindracea Pennant (1039), 1057 1053, 1054, 1055, 1058, 1059 (36) hW;20 (13), (14), (40), 1058 (13), (14) 1039 (13), (14),1033, (1034), 1039, 1057, 1068 (6), 14, 1034 (40), 1057, 1058, 1059 (14) 1039, 1068 (6) (6) (6), (35), (40), 1039, (1056) 1033, 1034, 1035, 1036, 1056, 1058, 1060, 1068 Minimum Depth-range fm (650)-775 312-(1202) (490)-(550) (775) (260) (220)-(660) 260-(314) 25-312 (220) 37-55 (240)-312 (220)-(240) 314 (220)-260- 509 220-489- (958) 260 220 (220) 208-312 (220) 295-314 (958) (958) (100)-314- (958) 100-1268 Off Grand Banks Labrador Sea (t) Off S. Greenland (t) Baffin Bay Off S. W. Iceland Materials and Methods ” a | To aoe ae c ) a. @- = ro e se) ce © > <= ” Eos = 5 = (40) : . -— = © s = . Species = =a me 5 . = ¥ a) Pe | oO a oO aa) e) fm 77. Cylichna propinqua M. Sars 1033, (1057), (260)-509 ~ ~ - t ~ (1068) 78. Scaphander nobilis Verrill (775) (775) (t) - - - - 79. Scaphander punctostriatus (6) (958) - (ft) - - as (Migh. & Ad.) Philinidae 80. Philene quadrata Wood 6 958 - Tt ~ ~ ~ Diaphanidae 81. Diaphana globosa Lovén (6) (958) - (ft) - - ~ 82. Diaphana hiemalis Gould 1068 295 - ~ - t - Aeolidiidae 83. Aeolidia sp. 17 37 - - ~ - t Scaphopoda Siphonodentaliidae 84. Siphonodentalium lobatum 1033, 1034, 295-509- - - - t ~ (Sowerby) (1060), 1062, (600) 1068 Dentaliidae 85. Dentalium agile M. Sars (23) (600) ~ - ~ - (ft) 86. Dentalium entale L 13, 14, 15, 16, 21 58-320 - - - - t 87. Dentalium occidentale (14), 1039, 1068 (220)—-295- - - _ H) (t) Stimpson 314 Pelecypoda Nuculidae 88. Nucula atacellana Schenck 6 958 - Tt - - - (= N. cancellata Jeffreys, non Meek) 89. Nucula belloti Adams 1058 312 - - - t - 90. Nucula delphinodonta 1033, 1034, 1038, 208-509 - ~ - 5 - Migh. & Ad. 1039, 1057, 1059, 1068 91. Nucula proxima Say 40 215 - T - - - 92. Nucula tumidula Malm 13, 14 220-240 ~ - ~ - Tt Malletiidae 93. Tindaria sp. (23) (600) - - - - @ Nuculanidae 94. Pristiglioma nitens (Jeffreys) 73 1918-2354 - - _ = 95. Ledella confinis (Smith) (6), (7) (958)—(2354) - - - - 96. Ledella messanensis (Seguenza) 6, 23 700-958 - is ate t 97. Nuculana minuta (Miller) (16), 1053, 1054, 25-95 = = T+ ae 1056 98. Nuculana pernula pernula (775) (775) 7). => - - - (Muller) Materials and Methods Species 99. Nuculana pernula costigera (Leche) 100. Nuculana sp. (juv.) 101. Yoldiella expansa (Jeffreys) 102. Yoldiella intermedia (M. Sars) 103. Yo/diella iris Verrill & Bush 104. Yoldiella lenticula (Moller) 105. Yoldiella lucida (Lovén) 106. Yo/diella sp. (juv.) 107. Megayoldia thraciaeformis (Storer) Arcidae 108. Bathyarca glacialis (Gray) 109. Bathyarca “pectunculoides” (Scacchi) 110. Bathyarca profundicola Verrill 111. Arca nodulosa Muller Limopsidae 112. Limopsis cristata Jeffreys 113. Limopsis minuta Philippi Mytilidae 114. Dacrydium vitreum (Mller) 115. Modiolus phaseolinus (Philippi) 116. Musculus discors laevigata (Gray) 117. Musculus nigra (Gray) Pectinidae 118. Cyclopecten abyssorum (Lovén) 119. Cyclopecten groenlandicum (Sowerby) 120. Cyclopecten imbriferum (Lovén) 121. Cyclopecten vitreum (Gmelin) 122. Chlamys furtiva (Lovén) 123. Chlamys islandicus (Muller) 124. Chlamys septemradiatus (Muller) Stations 1056, (1059) (40) (1034) (40), 1033, 1034, 1039, 1057, 1058, 1059, 1060, 1062 (23) 1057, 1058, (1059) 40, 1033, 1034, 1039, 1054, 1057, 1062, 1068 (13), 14, (23), (26), (32), (35), (37), 1035, 1036, 1061, 1064 9 21, 36 (13), (14) 6, 13, (23), (26), (32), (35), 775 6, 1039, 1057, 1058, 1062 16, 17, 20 1053, 1054, 1056, 1069 1056 1039 (13), (14), 1034, 1038, 1062 (23), (26), (35), 1062, (1038), (1068) 775 (14) (29), (36), (1054), (1069) (13), (14), (21), (23), (29) Minimum Depth-range fm 100-(208) (215) (489) 208-600 489 360 220-958 (600) (208)—260- 312 25-509 220-1280 1918 320 (220)-(240) 240-958 260-958 37-86 25-95 95 314 (220)-360- 489 (295)-360- (620) 775 (220) (25)—(260) (220)—(600) Off Grand Banks Labrador Sea (t) Off S. Greenland (t) Baffin Bay Off S. W. Iceland Materials and Methods ” TD T Sas £2 E ® faa) oO (= ® 1©)) io) oO Ss) = = be es © a c te © 7" Oo aa = Species = E = 6 2S « “fa S Eo = Lg SS Sa a =a oS 6% a3 fm 125. Chlamys striatus (Miller) (20) (55) - ~ ~ - (ft) 126. Hinnites distorta (da Costa) 17, (20) 37-(55) - _ = = + Limidae 127. Limatula elliptica Jeffreys (35) (405) - vi af): ailbes = 128. Limatula hyperborea (Jensen) 6, 13, (23);-1039, 240-958 - 03 _ t t 1068 129. Limatula subauriculata 14 220 ~ - - - +t (Montagu) 130. Limatula louiseae (n. sp.) 9 1918 - G) ~ - - 131. Lima (Acesta) excavata (23), (31) (680) - -— (t) - (t) (Fabricius) Anomiidae 132. Monia patelliformis (L) 17, (20) 37—(55) ~ - ~ - + 133. Anomia aculeata Muller 29 260 ~ - t - - 134. Anomia ephippium L 16 86 - - - - 3 Astartidae 135. Astarte borealis (Schumacher) 1054, 1056, 1057, 25-312 - ~ - + - (1058), 1059 136. Astarte crenata Gray 13, (16), (20), 21; (30)—240- - ~ t | (t) 29, (32), (35), 489-(1210) (37), 1034, 1039, 1057, (1059), (1061), 1068, (1069) 137. Astarte elliptica Brown (1069) (30) - - (t) - ~ 138. Astarte montagui (Dillwyn) 1054, 1057, 1059 25-260 - - - t ~ 139. Astarte subaequilatera 13, 14 220-240 ~ - - - tT (Sowerby) Thyasiridae 140. Thyasira equalis(Verrill&Bush) 1033, 1034, 1036, 209-1268 - - ~ t - 1059, (1060) 141. Thyasira gouldi Philippi 40, 1039, 1057, 208-314 ~ tT = t ii 1058, 1059 142. Axinulus eumyarius (M. Sars) 6 958 - f pee 143. Axinulus ferruginea 13, 14 220-240 - ~ - - } Winckworth 144. Axinulus pygmaeus 1033, 1034 489-509 - - - 4) ~_ (Verrill & Bush) 145. Axinulus succisa Jeffreys 6 958 - t a OR gD? a 146. Axinopsis orbiculata G.O. Sars —_ (13), 1059 208-(240) - - = t2on-Ghi Erycinidae 147. Kellia suborbicularis(Montagu) 17 37 > Woe) |) saloon Cardiidae 148. Serripes groenlandicus (35), (1054) (25)-—(405) =~ = i “ae (Gmelin) 10 Materials and Methods Species 149. Clinocardium ciliatum (Fabricius) 150. Parvicardium ovale (Sowerby) 151. Parvicardium scabrum (Philippi) 152. Cerastoderma elegantulum (Beck) Veneridae 153. Venus casina L 154. Venus (Timoclea) ovata Pennant Mactridae 155. Spissula elliptica (Brown) Psammobiidae 156. Gari fervensis (Gmelin) 157. Gari (Psammobella) tellinella (Lamark) Semelidae 158. Abra nitida (Muller) Tellinidae 159. Macoma calcarea (Gmelin) 160. Macoma loveni (Jensen) 161. Macoma moesta (Deshayes) Hiatellidae 162. Hiatella arctica (L) Myidae 163. Mya truncata (L) Thraciidae 164. Thracia myopsis ‘‘Beck” Moller Laternulidae 165. Periploma abyssorum Verrill Verticordiidae 166. Lyonsiella abyssicola M. Sars 167. Lyonsiella sp. Stations (1054) (16), (20) 13, 14, (16) 1054 20 14, 20 16, 17 15 16, 20 14 1053, (1054), 1055, 1056, (1069) 1056, (1059) 1053, 1054, (1055), 1056 16, 17 (1052), 1053, 1054, (1055), 1056, 1069 (1052), 1054, (1069) 1059 1059 1033 1039 Minimum Depth-range fm (405) (55)—(86) (86)—220- 240 25 55 55-220 37-86 58 55-86 220 (25)-92-95 95-—(208) 25-95 30-95 (0)—25-(30) 208 208 509 314 Off Grand Banks Labrador Sea Off S. Greenland (t) (t) Baffin Bay Off S. W. Iceland (t) t —+ + 11 Materials and Methods g Z Z = o oc w Se = = f S = O fea) = Species 2 E< 5 £¢ 6 £ae S = a a ” =O O a O co Oo fm 168. Verticordia sp. 1069 30 - - " ~ - Poromyidae 169. Cetoconcha nitida (Verrill) 775 775 t ~ - - - Cuspidariidae 170. Cuspidaria exigua Jeffreys 23(?), 1034, 360-1000 eee Ch) (2) 1062, 1065 171. Cuspidaria glacialis G. O. Sars 26, 40(?), 1033 215(?)- - (?) - (iene (509)-(620) 172. Cuspidaria lamellosa (M. Sars) 1039, 1068 295-314 - - ~ ~ 173. Cuspidaria pellucida 1034, 1062 360-489 ~ - - - Stimpson 174. Cuspidaria subtorta (G.O. Sars) 1057, 1059 (208)-260 - - =. Giaare 1. Numbers and symbols without parentheses — indicates absence or failure to detect presence; fap FeSghe ivune SPeCHeRns: Symbols within circles indicate new _ regional Numbers and symbols within parentheses _ records; represent empty shells; ? indicates uncertain identification (usually juve- t indicates presence; nile specimens). 12 Taxonomy Most of the species collected during this survey have been discussed and illustrated in the relevant literature, for example, Sars 1878; Thorson 1941, 1944, 1951; Madsen 1949; Ockelmann 1958; Tebble 1966; Mac- pherson 1971; Lubinsky 1972. It is therefore unnecessary to discuss them all here. How- ever, some of the species appear to be new, and others exhibit unusual morphological features or contribute to the solution of tax- onomic problems. The following remarks pertain to such species. Lepidopleuridae Smith (1960) has shown that Stenosemus Middendorff, 1847, is-an available generic name, with Chiton albus Linnaeus as its type species. Lophyrochiton Yakovleva, 1952 (type, C. a/bus L.), is therefore an objective synonym, and the species called Lophy- rochiton albus by recent authors is here cited as Stenosemus albus. The specimens of S. albus reported here were taken off southwestern Iceland in 86 fathoms and they show unusual variation. The four specimens form a series progressing from almost pure white with some brown mottling on the pos- terior valves to heavy chestnut with rust-red mottling on all valves (Figure 1). Patellidae The single specimen of Pilidium fulvum is an empty shell but with adherent periostracum. It is of the rare white “variety”’. Trochidae The Solariella obscura is an empty, half- grown specimen but is referable to ‘‘variety”’ bella Verkrizen as illustrated by Odhner 1912. Trichotropidae Six specimens of Torellia were collected alive off the Grand Banks in 775 fathoms. They are exceedingly variable in regard to periostracal “hair”, but the extreme speci- mens are connected by intergrades (Figures 2, 3, and 4). One extreme is evenly covered with short, fine hair. This is much like the figures in Jeffreys (1867, Pl. 4, fig. 1) and Sars (1878, Pl. 22, figs. 1a, 1b) of Torellia vestita Jeffreys except that the spire is some- what lower, as noted by Verrill (1882:521). The other extreme is densely covered with long, flat hairs arranged in ten spiral rows on the body whorl. This is undoubtedly the T. fimbriata of Verrill and Smith (Verrill 1882:520, Pl. 57, fig. 27). Some of the inter- mediate specimens also match Verrill’s de- scription of Torellia fimbriata var. tiarella (Verrill 1882:521). It is quite apparent that only one species is represented in our material, and the relatively smooth specimen is so much like the descriptions and figures of 7. vestita that it undoubtedly is that species. Therefore, both T. fimbriata Verrill and Smith and var. tiare//a Verrill must be regarded as synonyms of T. vestita Jeffreys at the species level. Whether or not a dis- Figure 1 Stenosemus albus (L), Sta. 16 Figure 2 Torellia vestita Jeffreys, Sta. 775 13 Taxonomy yy RV atiest ers wet Figure 3 Torellia vestita Jeffreys, Sta. 775 crete North American subspecies exists must remain unknown until much more material can be acquired and studied. Naticidae The Natica clausa from Station 15 is unusual in that it is reddish-brown, with a distinct white band below the suture and white on the base. See Odhner 1913:14 for an exten- sive description of variation in N. clausa. 14 1mm | Figure 4 Torellia vestita Jeffreys, Sta. 775 Pyramidellidae Melanella orphanensis, n. sp. Figure 5 Description Shell small (about 1/6 inch), turriculate, white, slightly bent, and with narrow axial riblets irregularly spaced on the early whorls. About nine whorls on holotype. Nuclear whorl deviated paucispiral. Early postnuclear whorls plano-convex, with a_ translucent band below the suture, a transparent band above the sutures, and with close but irreg- ularly spaced white axial thickenings be- tween the suprasutural and subsutural bands. Late postnuclear whorls predominantly flat but noticeably convex above sutures and with axial thickenings fewer but extending to both sutures. Sutures impressed. Body whorl with a poorly defined, low, subangular spiral peripheral band and a similar spiral band below it intersecting the top of the aperture. Spire narrow and slightly bent. Aperture small, prosocryt, orthocline, mostly basal, angular above, sharply convex below; outer lio narrow and evenly curved; inner lip thickened and intersecting the columella within the aperture. Umbilicus absent. No operculum seen. Holotype: height, 4.2 mm; width, 1.3 mm; number of whorls, 9. Taxonomy Figure 5 Melanella orphanensis (n. sp.), holotype, Sta. 6 Types Only the holotype is known and this is an empty shell in fine condition except for a small chip near the base of the outer lip. The specimen was dredged in the Labrador Sea on Orphan Knoll at Station 6 (50°32.9’/N, 46°22.0’W, 961 fm) by Mr. Brian T. Kidd on 23 May 1971. It bears catalogue number 66345 and is in the National Museum of Natural Sciences, Ottawa. Remarks | cannot locate any other species that has the bent spire and ribbed axial sculpturing of M. orphanensis. Nothing like it has been seen in museum collections in eastern North America or in the literature. The bent spire is Figure 6 Pyramidella sp., Sta. 6 characteristic of Melanella but, with the exception of growth lines, none of the species known to me possess axial sculptur- ing. The axial sculpturing is quite distinctive, and the holotype therefore appears not to be a deformed specimen of any species that is normally not bent. The species may deserve separate supraspecific status but more ma- terial should be available before that deci- sion is made. A single Pyramidella was also taken at Station 6. The specimen was dead, some- what worn, and its aperture was occupied by a sipunculid worm tube. The mollusc appar- ently belongs to an undescribed species but its condition is not good enough to provide a suitable basis for description of a new species. The specimen, with the sipunculid tube removed, is shown in Figure 6. 15 Taxonomy Figure 7 Tindaria sp., Sta. 23 Malletiidae A single valve of Tindaria was taken at Sta- tion 23 (61°36.6’N. 28°25.7’W, 600-700 fm) on the Reykjanes Ridge using a rock dredge. It also appears to be an undescribed species but is too incompiete to describe. The speci- men is illustrated in Figures 7 and 8. 16 Figure 8 Tindaria sp., Sta. 23 Limidae Limatula louiseae, Nn. sp. Figure 9 Description Shell minute (about 1/10 inch long), similar in shape to other species of Limatula, in- flated, thin, fragile, translucent and concen- trically ribbed. Sculpture consists of about 30 sharp, narrow, concentric ribs, a few of which are wider than the others and are lamellate; poorly defined whitish, radial streaks across the central portion of the valves; and fine whitish lines on the anterior and posterior slopes approximately perpen- dicular to the hinge line and diagonally intersecting the concentric ribs. Umbones rounded, projecting beyond the hinge, and with centrally worn apices apparently caused by mutual abrasion when the valves are opened. Auricles short and equal. Hinge straight, with ligament pit shallow, centrally located, V-shaped above, rounded below, and projecting below the hinge line. Interior whitish, with external ribs and lines clearly visible. | Holotype: length, 2.3 mm; width, 1.6 mm; inflation (valves appressed), 1.6 mm. Taxonomy are tS areas PCE AY Pte LS SADA aS Re to Figure 9 Limatula louiseae (n. sp.), holotype, Sta. 9 Types The holotype, a living specimen, was dredged by Mr. Brian T. Kidd on board U.S.S. Lynch at Station 9 (51°06.6’N, 37°47.3’W, 1,918 fm) in the Labrador Sea not far from the western foothills of the Mid-Atlantic Ridge. It is in the Mollusc Unit, National Museum of Natural Sciences, Ottawa, and bears catalogue num- ber 66418. Limatula Iouiseae is named in fond memory of the late Louise Robinson Clarke, my good wife and dear friend, for 25 years. Remarks This small Limatula differs from L. elliptica (Jeffreys), L. subauriculata (Montagu), L. subovata (Jeffreys) and all other northern species seen, in that its dominant sculptur- ing is concentric and not radial. The species cited, and other species, also exhibit con- centric lines but none have the prominent lamellate cords of L. /ouiseae. |t is closer to Limatula laminifera (Smith) than to any other Known species, but it is more equilateral and has microscopic lines on the anterior and posterior slopes diagonal to the lamellae, a feature that apparently (Stuardo 1968) does not occur in L. /aminifera. In addition, L. laminifera is from mid-archibenthal depths in the West Indies. Thus, on zoogeographic grounds alone it is unlikely that the two populations represent the same species. Limatula louiseae was found in somewhat deeper water than the deepest previous record for a Limatula, that is, L. subauriculata in 1,785 fm (Clarke 1962). It may be an im- mature specimen but, if so, appears to be quite different from the young stages of any other North Atlantic species. a7 Taxonomy -——————— 1mm teint sent ener ernen ante meen —ereenavmernmenstsnmrrent| 1mm Figure 10 Figure 11 Lyonsiella sp., Sta. 1039 Lyonsiella sp., Sta. 1039 Verticordiidae Two small living specimens of Lyonsiella were found at Station 1039 (66°10.5’N, 57°33.6’W, 314 fm) on the saddle of the Davis Strait Sill. They do not appear to belong to any known species, but since they are ap- parently quite immature their identity cannot be established with certainty. (Figures 10 and 11). 18 Range Extensions Several of the species found represent sub- stantial range extensions. These species with the exception of those which have already been discussed or have not been confidently identified, are listed below. Pilidium fulvum (Muller) occurred as a fresh, empty shell off southern Greenland in 550-650 fm. The species is recorded from Iceland and farther east (Thorson 1941) but not from the North Atlantic west of Iceland. Calliostoma occidentale (Mighels and Adams) was found alive off southern Green- land in one dredge haul taken in 220-400 fm. it was previously known only from North America (off Sable Island, Nova Scotia, to off New Jersey) and Europe (northern Nor- way to Scotland) (Clench and Turner 1960). Cerithiella metula (Lovén) was taken alive in Davis Strait and the Labrador Sea and as empty shells off southern Greenland and southwestern Iceland. The species was known previously only from Iceland eastward (Thorson 1941). Laeocochlis granosa (Wood) occurred off the Grand Banks (empty but fresh-looking), in Davis Strait (alive and dead), and off southern Greenland (dead but fresh). Sars (1878) recorded it only from the Norwegian Sea, but Thorson (1941) later recorded it from West Greenland (alive) and Iceland (shells). It has not been recorded previously from off the coast of North America. Acirsa costulata (Mighels and Adams) was found, as empty shells, in the Labrador Sea and off southwestern Iceland. It was pre- viously known only from West Greenland and the coast of North America south to Massa- chusetts (Clench and Turner 1950). Epitonium obtusicostatum (Sars) was taken, shells only, on the Reykjanes Ridge southwest of Iceland and off southern Greenland. Thorson (1941) recorded empty shells from Iceland and Norway (no living specimens) but not west of Iceland. Aclis walleri Jeffreys was collected empty from the Reykjanes Ridge off southwestern Iceland. It is recorded from off Norway (Thorson 1941) and from the Labrador Sea (Thorson 1951) but not Iceland. Neptunea satura (Martyn) was found alive and as empty shells off southwestern Iceland. The species is not listed from Iceland by Thorson (1941). Golikov (1963) gives the range of N. satura as extending from the coast of Yukon Territory to southern Alaska and Kamchatka and across the arctic coast of Eurasia to Finland and Spitzbergen. The Iceland records apparently represent the farthest extension into the North Atlantic that this species has so far achieved. Eulimella compactilis Jeffreys was col- lected alive from two localities in the central part of Davis Strait. Thorson (1944) records this species in the North Atlantic only near or south of Lofoten Is., Norway. Ledella confinis (Smith) was found, as empty shells, at two localities in the Labra- dor Sea in 958 and 2,354 fm. It was known previously only from the Mid-Atlantic Ridge and the Canaries Basin in depths of 410- 1,150 fm (Clarke 1962). Arca nodulosa Muller occurred alive southwest of Iceland and near Cape Fare- well, Greenland. It has not previously been recorded west of Iceland (Madsen 1949). Cyclopecten abyssorum (Lovén) was found living in 314 fm in Davis Strait. Previous records are all from the eastern Atlantic from the Norway Basin south to the Cape Verde Basin (Clarke 1962). Chlamys septemradiatus (Muller) was found as empty shells southwest of Iceland (including a locality on the Reykjanes Ridge) and near Cape Farewell, Greenland. It was recorded by Madsen (1949) only from Iceland and eastward to the coast of Europe. Axinulus pygmaeus (Verrill & Bush) was found abundantly at two localities in north- western Baffin Bay at 489 and 509 fm. It was Known previously only from the North Ameri- can Basin and near Iceland (Ockelmann 1958). Cuspidaria exigua Jeffreys was found alive in three dredge hauls from northwestern and east-central Baffin Bay and occurred empty (identification uncertain) southwest of Ice- land. It has been recorded only as empty shells from the vicinity of Jan Mayen, Spitz- bergen, and Norway (Ockelmann 1958). Cuspidaria pellucida Stimpson occurred alive at two localities in northwest and east-central Baffin Bay in 360 and 489 fm. Ockelmann (1958) records it only from off North America between Newfoundland and Cape Cod. Cuspidaria subtorta (G.O. Sars) was col- lected alive at one locality and empty at another, both in northern Baffin Bay. It was previously recorded doubtfully from West Greenland and the coast of North America between Newfoundland and Cape Cod, and recorded positively from East Greenland eastward to off the coast of Europe (Ockel- mann 1958). 19 Range Extensions Some other species are recorded here from localities in Baffin Bay that are signif- icantly farther north than those previously known. The most extreme examples are Oenopota reticulata (Brown), previously known (doubttfully) from near Frobisher Bay (Macpherson 1971) and now recorded 600 miles to the north, and Megayoldia thraciae- formis (Storer), Known previously as far north as Upernavik, Greenland (Thorson 1951), and here recorded from localities 300 miles farther to the north. 20 Zoogeography At first sight the molluscan fauna dredged near Iceland appeared quite different from those dredged in Baffin Bay and along the coast of North America. Further examination showed the presence of several genera and species that do not occur in the western Atlantic, for example, Emarginula fissura, Aporrhais serresiana, Nassarius incrassatus, Arca nodulosa, Modiolus phaseolinus, Chlamys septemradiatus, Hinnites distorta, Parvicardium spp., Venus casina, Gari spp., etc. Immediate questions arose, such as, where does the transition zone occur be- tween the European and North American fauna;' how complete is that transition; and if a well-defined zoogeographic boundary does exist along the northern North Atlantic island arc, what biological, historical and oceanographic features maintain it? Analysis of the available distributional data on northern prosobranch gastropods (Thorson 1944: 146-54) and northern lamelli- branchs (Ockelmann 1958: 194-201), with additions from the present survey and other data, substantiates the casual observation that a well-defined transition zone exists between Iceland! and eastern Greenland. If the 79 pan-boreal Atlantic prosobranch species and the 70 pan-boreal Atlantic lamellibranch species (which occur from North America to Europe and along the whole Greenland-Iceland—Faroes island arc) are set aside, and the few species endemic to a particular segment of the arc are like- wise excluded, a substantial residue of North American species and European species remains. Not surprisingly, these species groups are represented by decreasing num- bers of species with the increasing distance from North America and Europe (Table 4). The faunal changes that occur may be expressed in a striking manner by noting the percentage of European species relative to the total of European plus North American species in the faunas of West Greenland, East Greenland, Iceland and the Faroes. These percentages are 22, 41, 88 and 100 respectively. The most dramatic shift occurs as one progresses from East Greenland to Iceland, and is caused principally by the large increase (78) of European species and only secondarily by a decrease (16) in North American species. On zoogeographic grounds, therefore, the island arc may be considered as a region of transition between the North American and European faunas; if it is desirable to apply a boundary line between these zoogeographic regions, the line should be located between East Green- land and Iceland. This problem should be expanded and investigated more thoroughly to determine whether or not corresponding zoogeographic boundaries may be defined for regions of greater depth. The whole problem of zoogeographic limits of the deep sea benthos is a particularly intriguing one. 1 | believe that such adjectives as “arctic”, “subarctic’’, ‘boreal’, and “European” have been applied much too extensively in the literature on marine molluscs. Pseudo-problems arise when one attempts to explain the presence of a species in the Arctic, for example, that has been assigned previously to a subarctic species group. In the present context, “‘European’” and ‘‘North Amer- ican” are used to characterize species whose distributions extend beyond the Greenland-Ice- land—Faroes arc to Europe or to North America. The terms are meant to imply nothing about species origins or about their migration routes, and no problems therefore arise through their use. Table 4 Species representation of geographic faunal groups of marine prosobranchs and lamelli- branchs occurring near West Greenland, East Greenland, Iceland, and the Faroe Islands West Species Group Greenland North American prosobranchs 27 North American lamellibranchs 16 European prosobranchs 5 European lamellibranchs Py Per cent North American* 21 Per cent European 6 Per cent pan-boreal Atlantic 73 East Faroe Greenland Iceland Islands 22 10 0 8 4 0 10 44 56 11 55 73 15 5 0 10 38 46 7§ 57 54 *Prosobranchs and lamellibranchs only and excluding localized endemic species. Discussion It is usually difficult, and often impossible, to decide whether new regional records for species are the results of more thorough and effective collecting methods or if they signify migrations of the species concerned. When large or conspicuous species are found in areas that have been well studied by previous investigators, it is probable that faunal mi- grations have occurred. Present examples are the new records of Laeocochlis granosa from near the Grand Banks, Neptunea satura from near Iceland, and Megayoldia thraciae- formis from the northern extremity of Baffin Bay. On the other hand, new records of small and inconspicuous species may not reflect faunal migrations, although the possibility of such migrations surely exists. Examples here are the new records of Aclis walleri, Euli- mella compactilis and Axinulus pygmaeus. Natural range expansions of some marine animals are well documented, and there is every reason to believe that the zoogeogra- phy of archibenthal and abyssal molluscs is also dynamic. Our present concepts of geographic distribution patterns of deep- water marine molluscs are based on summa- tions of all presumably authentic species records accumulated over 50 to 100 years or more. The extent to which these concep- tual patterns reflect present reality is an important question that deserves extensive investigation. Some aspects of the composition and re- lationships of the Baffin Bay molluscan fauna have been discussed previously (Thorson 1951; Clarke 1963). The material now available shows that the Baffin Bay fauna is substantially an extension of the Labrador Sea fauna but that it contains fewer species. The presence of some endemic mollusc species occurring in depths greater than 300 fm, that is greater than the sill depth of Davis Strait, suggests substantial antiquity of isolation of that fauna. These species are Acrybia glacialis Thorson, Colus krampi (Thorson), and some other species reported here that may be new, that is, Proneomenia sp., Chaetoderma sp. and Ly- onsiella sp. Presumed antiquity is in agree- ment with the most recent estimates of age for the termination of sea-floor spreading in Baffin Bay and the formation of the Davis Strait Sill, that is, about 60 million years ago (Keen et al. 1972; see also Hyndman 1973). Based on estimates of evolutionary rates derived from studies of other regions, the relative extent of endemicity in Baffin Bay is 22 lower than might be expected. Evolution may well be slower in cold than in warm regions, however, because as indicated by other ev- idence (Dobzhansky 1950, general; Clarke 1965, molluscs), selection in cold regions is primarily physical, whereas in warm regions it is primarily biological. Additional geophys- ical studies in Baffin Bay may well provide a new basis for estimating probable evolu- tionary rates in an arctic marine environment. References Cited Baily, J. L., Jr. (1961). A new name for Buccinum tenue Gray, 1839, preoccupied. Veliger 3(4): 93-94. Clarke, A. H. (1962). Annotated list and bibliography of the abyssal marine molluscs of the world. Nat. Mus. Can. Bull. 181: 114 pp. (1963). On the origin and relationships of the Arctic Ocean abyssal mollusk fauna. XVI Int. Congr. Zool. Proc. 1: 202. (1965). The scallop superspecies Aequipecten irradians (Lamarck). Malacologia 2(2): 161-88. (1972). The arctic dredge, a benthic biological sampler for mixed boulder and mud substrates. J. Fish. Res. Board Can. 29(10): 1503-05. (1973). Aspects of molluscan zoogeography in Baffin Bay and the Greenland Sea. Amer. Malacol. Union Annu. Rep. Bull. 1972: 31-32. Clench, W. J. and Turner, R. D. (1950). The genera Stenorytis, Cirsotrema, Acirsa, Opalia and Amaea in the western Atlantic. John- sonia 2(29): 221-48. (1960). The genus Calliostoma in the western Atlantic. Johnsonia 4(40): 1-80. Dobzhansky, T. (1950). Evolution in the tropics. Amer. Sci. 38(2): 209-21. Golikov, A. N. (1963). Univalve molluscs of the genus Neptunea Bolten [in Russian]. Akad, nauk SSSR Zool Inst. Fauna USSR, n.s. 85, 5(1): 1-217. Hyndman, R. D. (1973). Evolution of the Labrador Sea. Can. J. Earth Sci. (10)5: 637-44. Jeffreys, J. G. (1867). British conchology, or an account of the Mollusca which now inhabit the British Isles and the surrounding seas. Vol. 4. John Van Voorst, London. 487 pp. Keen, C. E.; Barrett, D. L., Manchester, K. S.; and Ross, D. I. (1972). Geophysical studies in Baffin Bay and some tectonic implications. Can. J. Earth Sci. 9(3): 239-56. Lubinsky, Irene (1972). The marine bivalve molluscs of the Cana- dian arctic. Unpublished Ph.D. dissertation, McGill University, Montreal. Macpherson, Elizabeth (1971). The marine molluscs of arctic Canada, prosobranch gastropods, chitons and scapho- pods. Nat. Mus. Can. Publ. Biol. Oceanogr. 3: 149 pp. Madsen, F. J. (1949). Marine bivalvia. Zool. Iceland 4(63): 1-116. Ockelmann, W. K. (1958). Marine Lamellibranchiata: The zoology of East Greenland. Medd. Gronland 122(4): 1-256. Odhner, N. H. (1912). Northern and arctic invertebrates in the collection of the Swedish State Museum. V. Prosobranchia, 1. Diotocardia. Kgl. Svenska Vetenskapsakad. Handl. 48(1): 1-93. 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