BIVALVES. ARCA. 51 



C. Marijui crenate, beaks recurved. 



*Lactea. Cucullus {Chambered A.) 



Nodulosa. Magellanica. 



Antiquata. Reticulata. 



Senilis. Candida. 



Granosa. ludica. 



Corbicula. Jamaicensis. 



Decussata. Campechensif. 



TEquilatera. Lata. 



Fallens. Senegalensis. 



D. Margin crenate^ beaks injlected. 

 Undata (Lettered A.) *Nucleus {Silverif A.) 



Pectunculus {S})otted A.) Rhomboidea. 

 Pectinata. Marmorata. 



*GIycymeri8 (OrhivularA.) Augulosa. 

 Pilosa. Scapha. 



Niimmaria. 



OSTREA.— Oyster and Scallop. 



Animal — a Tethys: Shellbivalve, generally with unequal 

 valvesj and slightly eared; hinge without teethy but fur- 

 nished with an ovate hollow, and mostly lateral trans- 

 verse grooves. 



There are no fewer than one hundred and thirty-six 

 species in this genus, and which constitute an inexhausti- 

 ble mine of endless beautv and variety. 



