ARCA. 173 



mens obtained by Sars and M f Andrew on the coast of 

 Finmark at depths of from 20 to 160 fathoms are smaller 

 than the Greenland shells; but those from our own 

 seas and more southern latitudes dwindle into insigni- 

 ficant proportions compared with any of the above. 

 M f Andrew has also dredged this species alive off Gib- 

 raltar, in 45 fathoms, and Forbes in the ^Egean, in 

 200 fathoms. Two specimens which I procured from 

 deep water off the north coast of Shetland were at- 

 tached by the byssus to tubes of Pomatoceros arietinus, 

 Miiller (Ditrupa subulata, Berkeley) ; and I kept one of 

 them alive for more than a day. Soon after it was put 

 into a glass vessel and had a fresh supply of water, it left 

 its plug of attachment on the Annelid case, and crawled 

 away at a fair pace on its narrow foot, the valves of its 

 shell spread out with the beaks uppermost. The action 

 appeared to be similar to that of Galeomma Turtoni. 



The shell has all the characteristics of Lamarck's 

 genus Cucull&a, the side teeth being nearly parallel 

 with the hinge-line, and consequently at almost a right 

 angle to the central teeth or crenulations. But this 

 angle varies in different individuals and at successive 

 periods of growth, and the position of the side teeth is 

 more frequently oblique than horizontal. The central 

 teeth are often wanting. I therefore abstain from 

 removing this species from Area, as well as from offer- 

 ing any opinion as to the value of Lamarck's genus. 

 Mr. G. B. Sowerby was the first to notice the inequality 

 of the valves in Cucull&a. 



Dr. Torell called my attention to the probability that 

 the present species might be identical with the A. 

 glacialis of Gray. Professor Sars had previously ex- 

 pressed the same opinion ; and in his Report on the so- 

 called glacial formation in the Diocese of Christiania, 



