6 MAHdlNELr-IP.T;. 



depressed, 1 •it'll rented in front to form short, triangular, flattened 

 and horizontal tentacles, and the eyes are at the lateral margins 

 of the head a little behind the bases of these tentacles; mentum 

 as broad as the head, but not extending beyond the tips of the 

 tentacles. The dentition (PI. 2, fig. 11) is essentially that of 

 MargineUa. Notwithstanding these differences of the animal, 

 I agree with Mr. Redfield, who has included Cystiscus Capensis in 

 his "Catalogue of MargineUa." It is A-ery probable that when more 

 specimens of the soft parts shall have been examined the result 

 will be the discover}- of many divergences from the structure 

 of the larger species which have furnished the family diagnosis. 

 Besides the Cystixcuii, other instances of variation from the 

 normal type of Marginellidas have been recently recorded. M. 

 de Maltzan has collected at Goree, coast of Senegambia, several 

 specimens of MargineMa glabella containing the animal. Some 

 of these are provided with a well-developed operculum, whilst 

 others (as diagnosed for the family) have none.* . Messrs. Crosse 

 and Fischer having examined the lingual dentition of one of 

 these operculated individuals, were surprised to find it differ 

 from that of all other Marginellte hitherto known, in possessing 

 lateral teeth, resembling Buccinum.f Maltzan has proposed a 

 new genus, Pseudomargwella, for the operculated shells ; which 

 he supposes to inhabit rocky shores, whilst the others live on 

 sand, at 15 to 30 fathoms ; although the evidence he presents of 

 this difterence of habit is insufficient. Two Pseudomarginellae 

 are described, one of which has an unguiculate operculum, that 

 of the other being lamellar, like Purpura ; they both possess a 

 narrow foot, with a small gland, and in one of them the tentacles 

 are short and broad, in the other short and round. All these 

 characters differ much from the broad foot, with large gland and 

 the long tentacles of the typical MargineUa — j^et the shells are 

 indistinguishable from that of the typical 3L glabella. 



Messrs. H. and A. Adams, in their " Genera of Recent Mol- 

 lusca," include the genus Pachybathron, Gaskoiu, in this family, 

 but its closer relationship with Cassididse Is very evident. The 



■ On the irregularity of development of opercula in Volutharpa, see this 

 Manual, vol. iii, p. 198. 



t .Tour, de Co^'^h . M ser., xx, 37.i, 1880, 



