409 
range of the molluscs foiind in these parts of tlie Atlantic and, as 
far as Pecten islandicus and Mytilus modiolus are concerned, in 
more Northern latitudes. The faet is that the named forms are not 
a heap of shallow-water forms which exclusivelj live near the low- 
water mark. On the contrary, they are on the whole forms which 
are 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. 
Depth at which 
the dead shells 
oceurred on the 
Kockall banks. 
The greatest 
depth at which 
the species are 
known to live in 
The vertical 
distribution of 
the species at 
the Norwegian 
the N.E. Atlantic. 
coasts. 
x\nomia patelliformis . . 
100 
— 
0—40 
Pecteii islandicus. 
100 
— 
5—136 
— tigrinus. 
100 
155 B.M. 
10-100 
Lima loscombii. 
100 
— 
5—650 
Mvtilus modiolus. 
100 
— 
0-100 
Cardium echinatum . . . 
ca. 100 
109 B. M. 
5-80 
Astarte sulcata. 
120 
690 B. M. 
5-300 
Dosinia lineta. 
100 
60 to 80 B. M. 
0—60 
Venus casina. 
100 
— 
10-60 
Mactra elliptica. 
100 
— 
10-50 
Thracia papyracea .... 
100 
•— 
10-60 
Mya truncata. 
100 
— 
0—107 
Saxieava arctica. 
ca. 100 
808 B.M. 
0-300 
Trochus millegranus .. 
120 
— 
10—100 
Bueeinum undatum . . . 
100 
— 
0—150 
Bueeinopsis 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- 
