364 Mr. Broderip and Mr. G. B. Sovverby on some 



The right valve is rather deeper than the left ; both are beautifully, 

 though very minutely decussated. The notch in the posterior edge is 

 placed just above the rather acuminated point. In Mr. Sowerby's col- 

 lection. 



Cytherea rosea. 



C testd oblique cordatd, subcornpressd, roseo-purpurascente^ concentric^ 

 sulcatd, antice lamellatd, lamellis remotis, postice spinis brevissi- 

 mis, latiusculis, muricatd ; long. 1/^, lat. -^qj alt. lyV> poll- 

 Hab. ad littora Oceani Pacifici. 



A species with ^rhich we have been long acquainted, but which has 

 been commonly regarded merely as a variety of C. Dione. It differs, 

 however, in so many characters that we do not hesitate to describe it as 

 a distinct species. From St. Bias. 



Venus Gnidia. 



F^. testd (Bquivalvi, sub-ventricosd, liris* concentricis, muricatis, dis- 

 tantibus, strias radiantes decussantibus, antice spinosioribus ; long. 



2^, lat. lt*o, a^t' Ir'o* Poli- 

 Hab. ad littora Oceani Pacifici. 



Lieut, Belcher dredged some fine specimens of this most elegant shell 

 near St. Bias. It has been known in this country for some time. It 

 is of moderate thickness, and the muricated concentric distant ridges 

 (the spines of which become more broad and developed towards the an- 

 terior end) beautifully cross the radiating striae which occur in pairs, with 

 a more narrow one intervening. The colour in fine specimens is a red- 

 dish fawn ; white inside, with a finely crenated margin. 



*Cyrena Mexicana. 



C. testd ellipticd, vcntricosd, utrinque rotundatd, antich breviore ; den- 

 tibus parvis, obtusis ; long, ly^, lat. |^, alt. lyV, poll. 

 Hab. in Mexico. 



From Mazatlan. Outside white, with an olivaceous epidermis ; inside 

 whitish, varied with reddish violet. In Mr. Sowerby's collection. 



* Lira, a ridg-e between two furrows. 



