409 
range of the molluscs found in these parts of the Atlantic and, as 
far as Pecten islandicus and Mytilus modiolus are concerned, in 
more Northern latitudes. The fact is that the named forms are not 
a heap of shallow-water forms which exclusively live near the low- 
water mark. On the contrary, they are on the whole forms which 
åre known to reach a depth of 50 to 100 fathoms, and some of 
them live even in the Atlantic at a depth of several hundred fathoms. 
The greatest The vertical 
depth at which | distribution of 
the species are | the species a 
known to livein | the Norwegian 
the N.E. Atlantic. coasts. 
Depth at which 
the dead shells 
occurred on the 
Rockall banks. 
Anomia patelliformis .. | 100 — 0—40 
Pecten islandicus ...…. | SE] OG — 5—136 
er 146 | 100 155 B. M: 10—100 
Lima loscombii ...... 100 — 5—650 
Mytilus modiolus .… | 100 — 0—100 
" Cardium echinatum ... | ca. 100 109 B.M. 5—80 
Åstarte sulcata .....…. | 120 690 B. M. 5—300 
Dosinia lineta ..…...…. | 100 60 to 80 B.M. 0—60 
Venus. Casina 5... 1 | 100 ……— 10—60 
Mactra elliptica ....… 100 — 10—50 
Thracia papyracea .... 100 i — 1060 
Mys fruness. 100 — 0—107 
Saxicava arcticå ....…. ca. 100 808 B. M. 0—300 
Trochus millegranus .. 120 — 10—100 
Buccinum undatum ... 100 — 0—150 
Buccinopsis dalei ..... 100 — 40—100 
To form a conception of the vertical distribution of the species I 
have in the above given list partly stated the greatest depth at which 
some of the species are found in a living state in the North-East 
Atlantic, (according to my investigations in British Museum, Natural 
History, of the Mollusca dredged during the ,,Porcupine" Expedi- 
tion,) partly quoted the vertical range of the species off the Nor- 
wegian coasts after the records of G.0.Sars (1. c. 1878), A. Nor- 
