274 OSTREADiE. 



defatigable Gmelin to reproduce it under many appel- 

 lations in his crude, but laborious compilation.* It is of 

 an abbreviated-ovate shape, scarcely at all oblique, and 

 almost equivalve. Both valves are moderately convex ; 

 the under, which is usually likewise the less darkly co- 

 loured, is rather the more shallow, but exhibits a sculpture 

 in no way differing from the upper one. The general 

 surface is radiated with numerous much-elevated ribs, 

 ranging from twenty-five to thirty in number, but usually 

 about twenty-eight, the profound interstices between which 

 are nearly of the same width as the costse, and, except when 

 highly magnified, appear smooth : under the lens, however, 

 they more or less distinctly exhibit very delicate striulse, 

 which upon the umbones are concentrically disposed, but 

 near the lower margin run from the sides of the ribs up- 

 ward in a somewhat divergent fashion, and usually form 

 angles at their junction. The costffi are abrupt at their 

 sides, and armed upon their rounded tops with erect and 

 somewhat vaulted linguiform scales, which are typically 

 rather large and not very approximate, and are usually 

 abraded near the umbones. The auricles are similarly sculp- 

 tured, but the scales upon the larger one of the under 

 valve, are more crowded and less elevated. The inequality 

 of the auricles is very considerable, the area of the larger 

 (which is of rather ample dimensions) being at least 

 thrice that of the smaller, and its upper or cardinal edge 

 about double. The entire length of the hinge-margin 

 is equal to, or a little more than, one-half the distance from 

 the beaks to the opposite margin. The auricular sinus 

 is large, subbiangulated, rather profound, and pectinated 



* According to M. Desliayes, the Ostrea muricata, jyimdata, aculeata, ochroleuca, 

 mustdina, flammea, incarnafa, versicolor, described and named by Gmelin from 

 almost irrecognizable figures of Gualtier, &c., all belong to this species. 



