CONCIIIFERA. 



221 



Venus thiara. 



usually found on sandy shores, in most seas; the rest 

 are fluviatile. 



(Marine genera, with the ligament external.) 



Venus. Lin. — Shell regular, closed, equi valve, mostly 

 somewhat inequilateral, varying from oval to triangu- 

 lar; in one valve three or four cardinal 

 teeth, in the other three teeth which 

 diverge, no lateral teeth, ligament ex- 

 ternal ; the pallial impression has gene- 

 rally a sinus behind. Animal, with the 

 mantle cloven in its entire length: 

 the siphons either connected or sepa- 

 rated : foot either compressed, broad, 

 small, or hatchet-shaped ; gills normal. 

 — Many species; also fossil. 



This genus, which is one of the most beautiful and nume- 

 rous amongst the Dimyaria, is found in all parts of the 

 world. The species V. Mercenaria, commonly in America 

 called the Clam, is cut by the North American Indians into 

 beads, of which they construct their wampum or treaty 

 belts ; the shells are also used amongst them as money, 

 and are made into ornaments for their dresses. V. thiara 

 (figured above) is very remarkable for the thin lamina 

 placed at regular distances on both valves, and is a very 

 pretty and delicate shell. The animals of most species 

 serve as food for man ; they lie buried in the sand, at a 

 short distance from the shore, and are most abundant in 

 hot climates. There are several British species. 



Philippi remarks that the animals and shells of this genus 

 present many essential differences; he does not approve 

 of the divisions made by Lamarck, into Venus with three 

 cardinal teeth, and Cytheria with four, but he thinks others 

 must unquestionably be made when they are more known. 



