LAMELLIBRANCHIATA. 



91 



Distribution. On the North American side Cypn'nn islaudica occurs from Cape Hatteras to 

 the Newfoundland Bank and the southern part of the Gulf of vSt. Lawrence '). On the European side 

 it is distributed from the south-west of France (Arcachon) to the Murmau Coast and White Sea^); 

 towards the west it reaches over the Faeroes to Iceland; from the Kattegat it reaches into the Sound 

 and through the Belts down into the south-western Baltic 3). Cypriva islaudica is consequently, as I 

 have already more fully shown on an earlier occasion t), a distinctly boreal form, a result that 

 Prof. Brogger has also come to from a consideration of its late immigration into southern Norway 5). 

 The vertical distribution is ca 4— 5ofni., but the young may be met with in greater depths''). 



In geologically very late (postglacial) deposits it has been found as far north as at vSpitzbergen, 

 which indicates that the climate of that time was somewhat milder than it is now?). 



Remarks. Gould & Binney write regarding Cyprina islaudica (op. cit. p. 131): "It is subject 

 to ver>- little variety". This does not agree with the experience I have gained on going through a 

 number of specimens from Iceland and the Fjeroes. I find, that the three dimensions of the shell 

 may vary considerably, as will be seen from the measurements given below. 



Height Breadth 



Locality Length Height Breadth — 



^ 6 6 Length Length 



Reykjavik 105 ■""-. 93 "•". 88.6 % 61.5 ""■. 58.6 7„ 



Vestmanhavn 104.5 - 89 - 85.2 - 51 - 48.8 - 



Keflavik 102.5 " 83.5 - 81.5 - 58 - 56.6 - 



Seydisfjordr 102 - 78 - 76.5 - S^ " 5° " 



Reykjavik 99 - 82 - 82.8 - 57 - 55-8 - 



0nundarfjordr 98.5 - 82 - 83.2 - 50 - 50.8 - 



Vidarvik 93 - 88 - 94.6 - 52 - 55.9 - 



1) Posselt (I.e.) gives it from Labrador and Packard as his authority, but it is not mentioned in the latter's 

 "View of the recent Invertebrate Fauna of Labrador" (Mem. Boston Soc. Nat. Hist, vol.1, Part U, 1867, p. 262), nor in the 

 later lists of the MoUuscau fauna of Labrador by W. H. Dall and Katharine Bush. The northern boundary for its occur- 

 rence at N. America is fixed, I find by the following statement of Wliiteaves: ".Although recorded by Fabricius as a 

 Greenland shell, this species has not yet been found in the Gulf of St. Lawrence, north of the Bale des Chaleurs" (Catal. of 

 the Marine Invertebrata of Eastern Canada, p. 130; Geol. Sur\-ey of Canada, 1901). W. is not right however in his reference 

 to Fabricius' Venus islandica (Fauna groenlandica, 1780, p. 4"), as this is obviously not identical with Linne's Vemis 

 (Cyprina) islandica, but with Cardium { Serripes) groenlandicum Chemnitz. 



2) Cat tie states, that it has also been taken in the eastern (the "cold") part of the Murman Sea |Les LanieUibran- 



ches du "Willem Barents". Bijdrageu tot de Dierkunde, 18S6), but Knipowitsch has never found it there (Zur Kennt- 



niss der geol. Gesch. der Fauna des Weissen und des Murman-Meeres, p. 24. Verhaudl. Kais. Russ. Mineral. Gesellsch. 

 St. Petersburg. 2. Sen, Bd. XXXVIU, No. i), so that it must be in any case extremely rare. 



3) In his lists showing the distribution of the MoUusca taken by the Swedish Expeditions of 1875 and 1876, Leche 

 has given C. islandica as occurring in the Bering Sea (K. Sv. Vet-Akad. Handl. Bd. 16, No. 2, 1S78, p. 81), and this statement 

 appears again in Posselt (L c); some mistake in writing or printing must have crept in here, as the species is not mentioned 

 in any of the lists published by Dall, Crosse, Edg. Smith or Krause on the MoUusca of the Bering Sea. 



4) Ad. S. Jensen: Studier over nordiske MoUusker. II. Cyprina islandica. Vidcnsk. Medd. naturh. Foren. Kbhvn., 

 1902, p. 33. 



5) Br5gger: Om de senglaciale og postglaciale nivaforandringer i Kristianiafeltet, 1900—01, p. 573. 



6) A. C. Johansen has shown, that smaU (young) specimens can be met with even in the abyssal region, as Jeffreys' 

 statement of the occurrence of C. islandica \V. of Ireland down to 1215 fm. refers to quite small individuals (Vid. Medd. 

 Naturh. Foren. Kbhvn., 1901, p. 44). 



7) a. my paper on Cyprina islandica I.e. and Jensen & Harder in: "Postglaziale Klimaveranderungen, Stockhohn 



1910, p. 400. 



12* 



