CONCHYLIA— l>JTHy/eJ. 28. lit 



sometimes nearly equilateral, and sometimes much produced and 

 sloping from tlie hinge on the hinder side ; sometimes quite plain 

 and coarse, with a strong flexuosity, often radiate with blood red 

 of a greater or less degree of intensity. 



28. LVCl^X— BR UGUIERE. 



Testa subotbicularis, eequivalvis, clausa. Cardo dentibus 

 duobus vel tribus in allerd dialed, cum fovea internd trans' 

 versd anticd : lateralibus nuUis. Liigamentum externum. 



Shell somewhat orbicular, equivalve, closed. Hinge with two or 

 three teeth in one of the valves, and an internal transverse 

 cavity on the anterior side : lateral teeth none. Ligament 

 external. 



Lamarck has, we think, made his character of this genus so 

 diffuse, as to compreiienJ species very discordant, and according 

 to our present ligamentous arrangement, essentially distinct. 

 Such, for example, as have primary teeth, and such as have none ; 

 some that are furnished with lateral teeth, and some that are 

 without them. 



His character also of the teeth becoming evanescent by age, 

 can hardly be received as a precise and certain mark : nor are 

 the muscular impressions, which he points out as being very 



