70 



BOREAL PROVINCE. 



assemblages ; and it appears to me that their distri- 

 bution is regulated not only by depths, currents, 

 &c., but by the nature of the bottom itself, the 

 mixture of clay, mud, pebbles, &c. Thus, for in- 

 stance, the same species of Amphidesma (i. e. Syn- 

 dosmya), Nucula, Natica, Eulima, Dentalium, &c., 

 which are characteristic of a certain muddy ground 

 at fifteen to twenty fathoms, are found together at 

 eighty to one hundred fathoms. Hence it appears 

 that the species in this region have generally a 

 wider vertical range than the littoral, Laminarian, 

 and perhaps as great as the deep-sea coral. The 

 last-named region is with us characterized in the 

 south by Oculina ramea and Terebratula, and in 

 the north by Astrophyton, Cidaris, and Spatangus 

 purpureus of immense size, all living, besides Gov- 

 gonice and the gigantic Alcyonium arhoreum, which 

 continues as far down as any fisherman's line can 

 be sunk. As to the point where animal life 

 ceases, it must be somewhere, but with us it is un- 

 known. As the vegetation ceases at a line far 

 above the deepest regions of animal life, of course 

 the zoophagous mollusca are altogether predominant 

 in these parts, while the phytophagous are more 

 peculiar to the upper regions. The observation of 

 Professor E. Forbes that British species are found 

 in the Mediterranean, but only at greater depths, 

 corresponds exactly with what has occurred to me. 

 In Bohauslan (between Gottenburg and Norway), we 

 find, at eighty fathoms, species which, in Finmark 



