90 MOLLUSCA. 



the pernae, which he styles CRENATULA. The hinge in this 

 genus presents only a row of pits for the ligament, which 

 makes it appear crenulated. The intermediate spaces are 

 not formed into teeth, neither is there any callosity, or 

 opening for the byssus. He has figured two new species, 

 which he terms avicularis and mytiloides, and a third is the 

 ostrea picta of Gmelin, (Chemn, Conch, vii. p. 243. tab. 38. 

 f. 575.) 



Nearly related to the pectens is the genus LIMA of Bru- 

 guiere. The species differ, however, in the ligament being 

 in a great measure on the outside. They are all of a white 

 colour. The ostrea lima is considered as the type of the 

 genus. 



The genus PEDUM of Bruguiere differs from the preced- 

 ing in the ligament being external, ad attached to a long 

 straight fissure. The ostrea spondiloidea of Chenin. { Conch. 

 viii. t. 72. fig. 669? 670,) is considered as the type of the 

 genus. 



To this family we must add two genera, possessed of very 

 singular characters. They have neither hinge nor ligament. 

 The first, instituted by the celebrated botanist, Commer- 

 son, is termed ACARDO. The valves are depressed and 

 nearly equal, and held together by the adductor muscle. 

 The species at present known come from the eastern coast 

 of Africa. The second is termed radiolites, and was insti- 

 tuted by Lamark. It differs from the former in the form 

 of the valves, the inferior being turbinated, and the supe- 

 rior convex or conical. The species occur only in a fossil 

 state, and Irave been long known to geognosts under the 

 title ostracites. 



15. ANOMIA. In the Linnaean system, this genus is equ- 

 ally faulty as the last. It contains many species, which 



