GENUS XIV. OSTREA. 77 



Mr. Pennant, Mr. Montagu, and several otliei's have sepa- 

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

 Lamarck divides this genus 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 muscular impression 

 on each valve (see Ostrea edulis'). 

 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 obliqviely 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, /. 40). 

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

 the hinge without teeth; cartilage internal, fixed in a 

 triangular hollow ; one muscular impression (see Ostrea 

 opercularis, f. 41). 

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

 the hinge toothless ; the cartilage external ; bealts distant 

 (see Ostrea Lima, f. 43). 

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

 beaks separated ; hinge without teeth ; the cartilage ex- 



