CASSIS. 



observation of some of our friends^ that it is frequently 

 found buried in the sand in company with some of the 

 common Mactrce, upon which it feeds. The state of our 

 knowledge not permitting us to unite Nassa with Cassis, 

 though we think it must be separated from Buccinum; 

 we shall be content with describing Cassis, and point out 

 the characters in which Nassa differs from it. 



Shell ventricose or inflated, frequently of a subtrigo- 

 nal form, the spire being generally very short. Aperture 

 longitudinal, narrow, in some species almost equal in 

 length to the whole shell, in others proportionally wider 

 and the spire being at the same time more produced, the 

 aperture can scarcely be considered as elongated. The 

 base of the aperture is produced into a short canal, which 

 is suddenly turned backwards, the inner edge of which is 

 rather acute and forms the twisted columella, the outside 

 of which is generally transversely plicated or rugose. 

 The outer lip when complete is thickened and turned out- 

 wards, in many species forming a varix at the completion 

 of each turn of the spire; and it is frequently also turned 

 inwards and dentated or grooved at its edge or inner 

 part. The inner lip also is thickened and expanded over 

 the lower part of the last volution, frequently forming a 

 flat expanded disk, extended beyond the edge of the last 

 varix, where varices are formed, and in those species 

 where no varices are produced till the full growth of the 

 shell, only spread over the ventricose part of the volution. 



The circumstances in which Nassa diff'ers from the 

 above, are, in having generally a longer spire; a shorter, 

 scarcely longitudinal aperture ; the canal, though reflected 

 in the same manner being shorter, and scarcely, if at all, 

 separated from the back of the shell; in never forming 

 any varix until arrived at its full growth; and in having' 

 its inner lip seldom so much expanded. 



The Cassides are numerous, frequently knobbed, 

 particularly at the upper part of the volutions ; variously 

 grooved, striated, cancellated, decussated, &c. They 

 are fine shells, and mostly inhabitants of tropical cli- 

 mates. The fossil species are not common, they belong 

 to the newer or tertiary formations. 



We have never seen the operculum belonging to this 

 Genus. 



