I 



CONCHTFERA. 473 



The shells of this tribe are remarkable for the elegance of 

 their forms and colours ; they are frequently ornamented with 

 chevron- shaped lines. Their texture is very hard, all traces of 

 structure beiDg usually obliterated. The Veneridce appeared first 

 in the Oobiic period, and have attained their greatest develop- 

 ment at the present time ; they are foiind in all seas, but most 

 abundantly in the f.roDics. 



Ventjs, L. 



Synonyms, Merceneria, Antigone, and Anomalocardia (flexuosa) 

 Schum, Chione, Megerle (not Scop.). Erycina (carioides), 

 Lamarck, 1818. 



Type, Y. paphia, L. PI. XX., Fig. 1. 



Shell thick, ovate, smooth, sulcated, or cancellated ; margins 

 minutely crenulated ; cardinal teeth 3 — 3 ; pallial sinus small, 

 angular ; ligament prominent ; lunule distinct. 



Animal with mantle -margins fringed ; siphons unequal, more 

 or less separate ; branchial orifice sometimes doubly fringed, 

 the outer pinnate; anal orifice with a simple fringe and 

 tubular valve ; foot tongue-shaped ; palpi small, lanceolate. 



V. textilis, and other elongated species, have a deep pallial 

 sinus ; V, gemma (Totten) has a very deep angular sinus, like 

 Artemis; V. reticulata has bifid teeth, like Tapes; V. tridac- 

 noides, a fossil of the United States, has massive valves, ribbed 

 like the clam-shell. The North American Indians used to 

 make coinage {tvampum) of the sea-worn fragments of Venus 

 mercenaria, by perforating and stringing them on leather 

 thongs. 



Distribution, 176 species. World-wide. Low water — 140 

 fathoms. V. astartoides, Behrings' Sea. V. verrucosa, Britain, 

 Mediterranean, Senegal, Cape, Eed Sea : Australia ? 



Fossil, 200 species. Oolites — . Patagonia, United States, 

 Europe, India. 



? Volupia rugosa. (Defrance, 1829.) Shell minute, Isocardia- 

 shaped, concentrically riJbbed, with a large lunule. Eocene^ 

 Hauteville. 



Saxidomus (Nuttalli), Conrad. Oval, solid, with tumid um- 

 bones ; lunule ; teeth 3 — 4, unequal, the central bifid ; 

 pallial sinus large. 



Distribution, 8 species. India, Australia, West America. 



Cytherea, Lam. 

 Etymology, Cytherea ^ from Cythera, an -^gean island. 



