Sowerby 's Genera, of Shells. 573 



figure of the bivalve covering of an animal of the genus Cypris. 

 This, though it does not strictly come within the province of the 

 Conchologist, is very appropriately introduced, since it is fre- 

 quently of considerable importance as a distinguishing mark of 

 particular strata. 



The Genera of Recent and Fossil Shells, for the use of Stu- 

 dents in Conchology and Geology. By G. B. Sowerby, 

 F.L.S. With original plates, by J. D. C. Sowerby, 

 F.L.S. Number xxiv. 



Of this work there has appeared since our last notice only one 

 number, which contains Oniscia N. G., Pyramidella, Pyrula, 

 Mactra, Lutraria, and Tornatella, together with the plate illus- 

 trative of the Genus Pholas. Oniscia, a genus established by 

 Mr. Sowerby, to receive the Strombus Oniscus of Linnaeus and 

 other congeneric shells, is thus characterized : " Testa oblonga, 

 subcylindrica, apice obtusiuscula, basi acuminata: Spira brevi; 

 apertura elongata, basi in canalem brevissimum desiuente ; labia 

 externa subincrassato, interne denticulato, mediane subcoarctato, 

 interno expanso, granulate :" and the species referred to it are 

 the O. oniscus, which was very unaptly arranged among the 

 Cassidariae by Lamarck ; the O. cancellata, an elegant and ex- 

 tremely rare species, a superficie externa lineis elevatis, cancel- 

 latis," now first described and figured ; the O. tuberculosa, a 

 new species just received from the South Seas ; and the O. Cy- 

 thara, a fossil from Italy, the Buccinum Cythara of Brocchi. 

 The characters of the genus Pyramidella are so enlarged as to 

 admit the Helix polita, Mont., and several similar shells, which 

 differ from the Pyramidella of Lamarck chiefly by the absence 

 of the plaits on the columella ; while those of Pyrula are con- 

 tracted to confine this genus to P. feus and the similar species 

 known in commerce by the name of fgs. The remaining genera 

 correspond with those of Lamarck, the only alteration of im- 

 portance introduced being in the description of the lateral teeth 

 of Mactra, which are stated by that distinguished Conchologist 



Vol. I. 2ft 



