CONCHYLIA— D/rHYi?^. xli 



3. discors, convexa, lateribus costatis, umbonibus terminalibus. 



convex, ribbed at the sides, with the beaks ter- 

 minal. 



4. discrepans, depressa, lateribus costatis, umbonibus sub- 



terminalibus. 



flattish, ribbed at the sides, with the beaks not 



quite terminal. 



45. OSTREA. 



1. Crista Galli, transversim squamosa, margine trigono-plicato. 



with transverse scales, and triangular plaits at 

 the margin. 



2. edulis, transversim squamosa, margine Icevi integerrimo. 



with transverse scales, and the margin smooth 

 and quite entire. 



3. parasitica, lesviuscula, parasitica. 



nearly smooth, and fixed to other substances. 



46. Pecten. 

 * auriculis subcsqualibus. 



with the auricles equal or nearly so. 



1. maximus, valvd superiori planatd, radiis rotundatis. 



the ujjper valve flat, with the rays rounded. 



2. Jacobseus, valvd superiori planatd, radiis angulatis. 



the upper valve fiat, with the rays angular. 



3. opercularis, radiis subviginti scabris. 



with about 20 rough rays. 

 *E 



