326 Mr. A. Hancock on Shells dredged on 



growth ; spire considerably produced, conical ; whorls seven or 

 eight, ventricose, the last one about half as long as the shell, oc- 

 casionally with a few distant obsolete spiral keels or ridges; 

 mouth roundish ovate, shorter than the spire, with the interior 

 of a deep rich glossy chocolate-brown, extending for a consider- 

 able way over the columella, which is smooth and regularly arched ; 

 outer lip thin and strongly lobed in front ; canal very short and 

 wide ; epidermis pale yellow, thin, horny, smooth and shining. 

 Length 2f inches ; breadth 1| inch. 



This fine species resembles in general habit the delicate, elon- 

 gated varieties of B. undatum, but is entirely destitute of longi- 

 tudinal plaits and is quite smooth. But were other characters 

 wanting, it might at once be distinguished from that, and from 

 all the other species with which I am acquainted, by the wide 

 spread of the enamel over the columella and body-whorl. It 

 would therefore appear that the mantle on the right side of the 

 •animal of B. hydrophanum is considerably more expanded than 

 in any of the allied species. The mouth, too, is broader than in 

 B. undatum, particularly in front ; the canal is shorter and much 

 wider, and the columella smoother and more regularly arched. 

 It also seems nearly related to B. Humphrey 'sianum and B. fusi- 

 forme of Kiener ; but differs from both in the character of the 

 columella and in the more rounded mouth ; also in the absence 

 of strise. 



The outer layer of shell in B. hydrophanum is very opake, white 

 and chalky, and is liable to be eroded : it is quite distinct from 

 the layer beneath, which is vitreous and of a vinous colour. The 

 keels or ridges on the body -whorl are irregular, and frequently 

 interrupted ; they vary in number from one to nine, and are oc- 

 casionally arranged in pairs : they are, however, frequently obli- 

 terated, and are never conspicuous, even in full-grown individuals. 

 The epidermis is confined to the body-whorl and readily peels 

 off. 



The most striking feature however of this species is the extra- 

 ordinary change in colour and appearance which take place on 

 the shell being immersed in water, when in a short time it loses 

 its opacity and becomes of a deep rich vinous hue. This ensues 

 immediately on the outer coat becoming saturated, which in this, 

 as in many of the Arctic shells, is very porous. 



In young specimens the outer covering of shell is very thin, 

 and the colour of the under layer is always more or less appa- 

 rent : in this state they have a bluish bloom, and are very deli- 

 cate and glossy. They are sometimes covered with minute spiral 

 strise ; and as the lines of growth are then very distinct, the whole 

 surface is sharply and finely decussated. As the shell increases 

 in size this appearance diminishes, and in half-grown individuals 



