48 



LAMELLIBRANCHIATA. 



Distribution. Mytilns cdulis has a wide range within the temperate, in part also the arctic 

 zone, both in the northern and southern hemispheres. In North America it occurs from North Carolina 

 to Labrador; next, it occurs on the western and south-eastern coasts of Greenland, at Iceland and 

 the Fteroes; from the west coast of Nova Zembla its distribution extends along the whole coast of 

 Europe, and also into the Mediterranean (var. galloproviiicialis Lam.) to its easternmost end; through the 

 Kattegat, decreasing in size, it reaches into the Baltic and up into the Gulf of Bothnia (to 62°6'N. L.). 

 In the Pacific it ranges from Bering Sea to the Sea of Okotsk, Japan and Mexico. In the southern 

 hemisphere the "Challenger" has taken it off Rio de la Plata, at the Falkland Islands, Kerguelen 

 and New Zealand. — It belongs to the littoral belt; I have some youug specimens, however, from 

 greater depths, down to 50 fni. ') 



In high-arctic regions the dead shells of Mytilns cdulis have been fovind at many places, where 

 in spite of the keenest search not a single living specimen could be taken. In Europe it does not 

 live north of Nova Zembla, yet dead shells occur in large numbers on Spitzbergen (both on the shore, 

 at the beach and in raised deposits), on King Charles Land (Svenska P'orlandet, 25 m. above the sea) 

 and on Franz Josephs Land (3— 6m. above the sea). At East Greenland, as mentioned, it does not 

 live N. of 66°3o'N. L., but it has been found as fcs.sil at ca. 73°N.L., namely at the mouth of vSophias 

 Sound (25 m. above the sea) and in the innermost parts of Franz Josephs Fjord (10 m. above the sea). 

 These discoveries of fossil (postglacial) Mytilns cdulis indicate, that the high-arctic regions mentioned 

 must have had a somewhat warmer marine climate than now at a not very remote geological period 2). 



Modiola modiolus Linne. 

 PI. Ill, figs. I a — b (young). 

 Mytilus modiohis Linne, Syst. Nat. ed. 12, i, 2, 1767, p. 1158; Jeffreys, Brit. Conchol. II, 1863, p. n, 

 PI. 27, fig. 2; (Modiola) Gould & Binney, Rep. In v. Mass. 1870, p. 186, fig. 485. — Mytilus 

 uinhilicatus Pennant, Brit. Zool., IV, 1767, p. 112. 

 Modiola umbilicata Morch, Viden.sk. Medd. Naturli. Foi'en. 1867, p. 96; ibid. 1868, p. 224. 



The "Ingolf" has taken this species at: 



St. 87. W. of Iceland (Brede Bugt) iiofm. i .spec, (empty). 



[Greenland]. 



The species is recorded from here by G. O.Sarss) and by Dr. A. Krause^). I have no hes- 

 itation in refusing to admit the correctness of these records; a bivalve of such a size and so easy to 

 get could not have escaped the attention of these, whose collections are preserved in the Copen- 



') N. Kn ipowi tsch (Verhandl. Kais. Russ. Mineral. Gesellscli. Bd, 43, 1906, p 271) mentions a few cases where he 

 has found Hving, full-grown Myt. edu/i's in great depths and at a constanth- very low temperature but at the same time ex- 

 presses agreement with a view 1 had put forward elsewhere (K. D. Vidensk. Selsk. Forhandl. 1904, p. 394), namely, that such 

 is not the normal habitat of the .species; the specimens in (piestion must be considered to have been carried out into the 

 deep, cold layers with seaweed, perhaps also with ice-floes (in the Kara Sea, for example, M. n/u/i's has been found on drift- 

 ice; of. Jensen 1. c). 



=) For further details see Ad. S.Jensen and Poul Harder: Post-Glacial changes of climate in Arctic regions as 

 revealed by investigations on marine deposits (Postglaziale Klimaveranderungeu. Stockholm, 1910, p. 399). 



3) Sars: Moll. Reg. Arct. Norv., 1S78, p. 387. 



4) Krause, in Griinland-Expedition der Gesellsch. f. F.rdkunde zu Berlin, II, i, 1897, p. 1S5. 



