247 



OSTREA: 



SHELL BIVALVE, WITH THE VALVES UNEQUAL AND 

 GENERALLY EARED : HINGE TOOTHLESS, WITH 

 AN OVATE FOSSULE, AND LITERAL TRANSVERSE 

 STRIyE. 



Subdivisions. ]" 



* Valves with the auricles equal. 

 ** Valves with the auricles unequal. 

 ### Valves more gibbous on one side than on the 



other. 

 * ## * Valves coarse and rugged. 

 =**#* With the hinge composed of transverse fur- 

 rows in a straight line. 



# Valves with the an rides equal. 



.maxima. 1. Shell with about fourteen rounded, 

 longitudinally striated ribs, and the upper 

 valve impressed between the auricles. 



t Besides several others which are elsewhere mentioned, the following of 

 Gmelin's species appear to he undeserving of notice : 



O. annulata, p. 3338. O. araia, p. 3327. O. aurantia, p. 3321. O, depressa, 

 p. 3330. O. exalbida, p. 3337. O.fuscii, p. 3320. O. innoinbmtn, p. 3329. O. 

 modesta, p. 3331. O. papyracea, p. 3337. O. principalis, p. 3331. O. rctusa, 

 p. 3338. O. seminuda, p. 3331. O. septemradiutu, p. 3327. O. spondyloidcs, 

 p. 3321. O. squamata, p. 3329. O. Valentini, p. 3329. O. violacea, p. 3321. 

 O. vittata, p. 3321. O. mytiloides, and O. <<?;*«, p. 3339, arc fossils, 



