MoUusca in the Collection of the Zoological Society. 371 



Margarita umbilicalis. 



M. testd obtuse conicd, obliqud, anfractibus sensim majoribus, longi- 

 tudinaliter striatis ; umbilico maximo ; long. ^%, lat.y%, poll. 

 Hob. in Oceano Boreali. 



Only one specimen of this interesting species has occurred. The 

 outer hp is much broken. 



Margarita striata. 

 M. testd conoided, anfractibus rotundatis, longitudinaliter striatis ; um- 

 bilico parvo ; long, -p^o, lat. -y\, poll. 

 Hab. in Oceano Boreali. 



The whole shell has a dull surface, its raised longitudinal striae are 

 decussated by very fine and close-set lines of growth : and those beneath 

 are much closer than those on the upper sides. 



*SlGARETUS CORIACEUS. 



S. testd ovali, tenuissimd, spird depressd, epidermide coriaced ; long. 

 ^f, lat. 1, poll. 

 Hab. in Oceano Arctico. 



We have placed this with Sigaretus on account of its similarity in 

 form, without any knowledge of the animal. It is remarkable for the 

 strength of the epidermis ; and such is the extreme tenuity of the shell, 

 that scarcely any vestiges of it remain when the specimen is dry, the 

 contraction of the epidermis causing it to scale off from the inside. From 

 Cape Lisbon Bay. In Mr. Bland's collection. 



Neritina alata. 



JV*. testd ventricosd, alatd, longitudinaliter striata, spirant versus obso- 

 lete transversim tri-sulcatd, nigrd, fulvo-varid ; aperturd albd ; 

 margine nigro ; columelld obsolete crenulatd ; long, -j^, lat -^^, poll. 

 Hab. in insula Taheite. 



The lip spreads out into a wing, projecting so far beyond the spire, 

 as to give that part of the shell an umbilicated appearance in old speci- 

 mens. From Taheite. 



