SHELLS. 237 



filaments to the proper place, and to glue them 

 there; and it can reproduce them when they have 

 been cut away ; but their true nature is not yet well 

 ascertained. 



The first family of the Acephala Testacea com- 

 prise the Ostrea, or oysters. As to the testaceous 

 Acephales, known in a living state, Linnaeus has 

 united under the genus Ostrea all those which have 

 neither teeth nor transverse lamina in the hinge ; 

 the valves being held together by a hgament lodged 

 in a little cavity on both sides. Among the species 

 common to our shores, we may notice the Ostrea 

 folium, the Ostrea crista galli, and the Ostrea 

 parasitica. 



To this family also belong the following genera, 

 viz. : — 



1. Genus Pecten. — The shells of this genus are 

 in general of a depressed form, more or less inequi- 

 valve, always eared, and almost always rayed longi- 

 tudinally by ribs more or less fine. The valves are 

 in general thin, of the same size, the upper one 

 being flattened. The species most usually found in 

 our bays is the Pecten concentricus. This is known 

 under the popular name of scallop, or scallop- 

 shell. 



2. Genus Area. — The A rcacece, or ark-shells, are 



