GENUS XIV. OSTREA. 77 



Mr. Pennant, Mr. Montagu, and several others liave sepa- 

 rated the Scallops from this genus, and called them Peclenes. 

 Lamarck divides this g-enus into six, as follow : 

 OsTREA. Shell adhering and inequivalved ; hinge without 

 teeth ; an oblong hollow with ridges across it for the re- 

 ception of the cartilage ; only one muscvilar impression 

 on each valve (see Ostrea edtilis^. 

 Malleus. Shell free, a little open near the beaks, fixing itself 

 by a byssus ; the valves equal ; the hinge without teeth, 

 a little swelling, and furnished with a conical hollow 

 for the cartilage, placed obliquely on the edge of each 

 valve, separate from the opening for the byssus (see Ostrea 

 Malleus, f. 39). 

 Perna. Shell flat and free, fixing itself by a byssus ; hinge 

 composed of several linear teeth, parallel and truncate, 

 not articulating, arranged obliquely or transversely on a 

 straight line; the interstices of the teeth in each valve re- 

 ceiving the cartilage (see Ostrea Ephippium, f. 40). 

 Pecten. Shell eared; valves unequal, with contiguous beaks; 

 the hinge without teeth; cartilage internal, fixed in a 

 tjriang-ular hollow ; one nmscular impression (see Ostrea 

 opercularis, f. 41). - 

 Lima. Shell inequilateral, eared, gaping a little on one side ; 

 the hinge toothless ; the cartilage external ; beaks distant 

 (see Ostrea Lima, f. 43). 

 Pedum. Shell eared; valves unequal, a little gaping; the 

 beaks separated ; hinge without teeth ; the cartilage ex- 



