CONCHYLI A— I>Jr//yi2^. xli. 



5. discors, conicxa, lateribus costatis, 7imbo7iibiis terminalibus. 

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

 minal. 



4. discrepans, depressa, lateribus costatis, wnbonibus 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 lavi integerrimo. 



with transverse scales, and the margin smooth 

 and quite entire. 



3. parasitica, Iceviiiscula, parasitica. 



nearly smooth, and fixed to other substances. 



46. Pecten. 



* auriculis subcequalibus. 



with the auricles equal or nearly so. 



1. maximus, vulva superiori planatd, radiis rotundatis. 



the upper valve flat, with the rays rounded. 



2. Jacobicus, valva superiori planala, radiis angulatis. 



the upper valve flat, with the rays angular. 



3. opercularis, radiis subviginti scabris. 



with about 20 rough rays. 

 • E. 



