the proposed Genus Cyprtecassis. 471 



&c; and if this condition continues, then it is that the animal 

 completes its mouth, giving to us those dwarf specimens so 

 common in cabinets. Upon cutting into several shells in this 

 state, there is no appearance of teeth, or even a raised ridge 

 upon the interior, while in the true Cassides each separate 

 period of its growth is as well determined by the teeth of the 

 outer lip, and the plicaa of the columella, as is the outer basal 

 face. 



In examining very numerous specimens, in their natural 

 state, of C. rufa and C. testiculus, I have not found the 

 slightest trace of epidermis ; and, indeed, to the want of this 

 protecting covering may be attributed the commonly eroded 

 state of the upper portion, or dorsum, of the shell in old 

 specimens. 



Whether it is the mantle or the foot which deposits the 

 thickened outer and columella lips, I shall not attempt to 

 determine, but merely state that the animal has a mantle 

 apparently as capable of secreting and depositing shelly matter 

 as that of any other mollusc. 



With respect to the operculum, I do not conceive that any 

 naturalist will dispute the fact, that the presence or absence 

 of this appendage to the animal is sufficient to ground a dis- 

 tinction beyond that of species only ; therefore, if we are, for 

 convenience' sake, to have the arbitrary divisions of subgenera, 

 genera, &c, surely it will be conceded in this case. 



From general resemblance, I was induced to claim C. co- 

 arctata *, among others, as species of this genus. Now, the 

 question remains as to whether Mr. Cuming may not by ac- 

 cident have applied the operculum of some other animal to 

 C. coarctata, since it is clear that C. testiculus has not an oper- 

 culum ; and, from the close approximation in form of these 

 two species, it is difficult to reconcile so close an affinity, with- 

 out expressing some doubt as to whether it is not possible 

 that such a mistake might have occurred. 



With regard to the young state of C. rufa, I have not 

 been so fortunate as to meet with specimens exhibiting the 

 conditions which Mr. Sowerby points out. I certainly never 

 have seen an instance in which the outer lip was completed 

 so far as to have a row of strong teeth, and an increase of the 

 volutions subsequently to have taken place. The figure given 

 by Mr. Sowerby, I imagine to be an animal just arrived at 

 that period of its growth when it would have completed its 



* Mr. Sowerby is correct in stating that I was misled by Kiener in 

 quoting Valenciennes for C. coarctata. I now recollect perfectly that a 

 description of this species did appear in the Tankerville Catalogue. 



M M + 



