GO^GRYUA—DITHYRA. 28. Ill 



sometimes nearly equilateral, and sometimes much produced and 

 sloijing from the hinge on the hinder side; sometimes quite plain 

 and coai-se, with a strong flexuosity, often radiate with blood red of 

 a greater or less degree of intensity . 



28. LUCm A— BRUGUIERE. 



Testa suborbicularis, cequivalvis, clausa. Cardo dentibus duobus vel 

 tribus in altera valvd, cum fovea interna transversa anticd: laterali- 

 bus nullis. Ligamentum 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 dif- 

 fuse, as to comprehend 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 



