BIVALVE SHELLS. 35 



8. Shell ovate, with decussate striae, angular before ; apex 

 turned to one side ; umbo placed nearest one end ; hinge fur- 

 nished vvith^three teeth in one valve ; posterior slope very minute 

 and retuse ; anterior slope long and narrow, with generally au 

 inner blue margin. The outside is commonly of a plain rusty 

 brown, and marked with purple zigzag lines. Two inches long 

 and three broad. Inhabits the British seas. 

 a Summit, e e cicatrix, g g g teeth of the hinge, n the inside. 

 Venus aurea. — The Golden Venus. Plate VI. fig. ]Q. 

 Suborbicular, inequilateral transversely striated, and striated 

 concentrically; of a fine golden -yellow. One inch long, one 

 and a half broad. Inhabits the British seas. 



The shells of this genus inhabit the ocean. They in general lurk iu thu 



gaud ; and many of the larger Bpecies are only to be found in very deep 



water. 



Genus ll.—SPONDYLUS. 



Animal a Tethys : shell hard, solid, and ridged, with unequal 

 valves ; one valve in general convex, and the other rather flat : 

 hinge with two recurved teeth, separated by a small hollow. 



The shells of this genus inhabit the ocean. They adhere to rofks iu deep 

 water, and require considerable force to tear them from their retreats. 



Spondijlus gcederopus. — The g^deropus Spondylus. Plate 

 VI. fig. 11. Upper valve red, under one white with longitudin- 

 al striae and ribs, rough granulations, and somewhat tongue- 

 shaped, truncated spines, which are rather short. Three inches 

 long. Inhabits the Mediterranean, and is considered excellent 

 food by the Italians. It is sold in the markets at Nice, and 

 other towns on the Mediterranean. 



Some of the Spondyli have ears, and others are devoid of 

 them ; they are in general strong, rugose shells. This genus 

 requires considerable attention, as some of the species are sub- 

 ject to such variety, that they are frequently mistaken for distinct 

 shells. 



Genus 12. — CHAMA. 



Animal a Tethys; shell bivalve, rather coarse; hinge with 

 a callous gibbosity, obliquely inserted into a slanting cavity ; an- 

 terior slope closed. 



Chama Cor. — The Heart Chama. Plate II. fig. 5. and 



