215 



oxoepting Dillwyn under the P. operculark, L. Mr. Conrad con- 

 siders the dislocatis as identical with the imrpuratus, Lam. Plate 

 56, fig. 2, 2a. 



NASSA.-Shell univalve, subovate, ventricose, or subturreted, 

 acute; aperture suborbicular, emarginated and reflected at base • 

 abium with a more or less dilated callosity or calcareous deposite • 

 labrum striated or sulcated within; operculum horny ; animal de^ 

 pressed : tentacula two, conie-cylindric, inflated at the eyes • eves 

 near the exterior middle of the tentacula ; proboscis very short or 

 obsolete; mantle folded into a distinct tube before; orifice of the 

 oviduct situated on the right at the opening of the branchial 

 cavity; branchia3 pectmiform, unequal, nearly parallel; male organ 

 on the right side of the neck; anus on the right; foot laro-e 

 prominent and angular before, attenuated behind 



Ohs^ Deshayes informs us that Klein first used this generic 

 term for some shells of a reticulated surface, having a fancied 

 resemblance to the "Nasse d'osier" or willow net of fishermen 

 J^amarck, however, first separated the present genus from the Lin- 

 n^^nBuccmnm, but has subsequently reunited it as a subgenus 

 In this arrangement many distinguished authors coincide, as 

 tuvier, Blainville, Ferussac (in his Tabl. Syst.) and Deshayes. 

 bowerby and some other naturalists still separate it as a distinct 

 genus nearly related to Cassis: Montfort carries the division still 

 furthei^ and divides the ^ssse into FJios, Alectrion and Cyclops 

 and Schumacher has also separated from it a few, species, under 

 the name of Nana, neither of which have been admitted by 

 the best authorities; and it is not improbable that iVa.sa itself 

 may be ultimately admitted universally as only a subgenus oi Bx,^- 



ctnum. 



The species are numerous and are both recent and fossil They 

 feed on animal food and they sometimes devour the animal of 

 some bivalve shells such as Tdllna altemafa, S., and one of the 

 valves of this species often exhibits a neatly formed, round per- 

 foration, near the umbo, bored by a mssa. These shells ' are 

 sometimes smooth, but more generally with impressed strict or 

 grooves; others are reticulated so as to appear granulated or tuber- 

 culated. 



A remarkable, depressed and even transverse species, the neintea 

 L., of which Montfort formed his genus (7ycfops, diflfers so much 



