CONCFIFERA. 463 



Batissa, Gray. Anterior lateral teeth short ; under ones long. 



Velorita, Gray. Anterior laterals thick and triangular. 



Bistrihution, 130 species. Tropical America (eastern), Egypt, 

 India, China, Australia, Pacific Islands. In the mud of rivers, 

 and in mangrove swamps, usually near the coast. C. consohrina 

 ranges from Egypt to Cashmere and China, and is found fossil 

 in the Pliocene formations of England, * Belgium, and Sicily. 



Fossil, 105 species. Wealden — . Eurone, United States. 



? Cykenoides, Joannis. 



Synonym, Cyrenella, Desh, 



Tyjje, C. Dupontii, PI. XIX., Fig. 19. 



Shell orbicular, ventricose, thin, eroded at IJtie beaks ; epi- 

 dermis dark olive ; ligament external, prominent, elongated ; 

 cardinal teeth 3.2, the central tooth of the right valve bifid; 

 muscular impressions long, narrow ; pallial line simple. 



Animal with the mantle open in front and below, margin 

 simple, siphons short, united ; palpi moderate, narrow ; gills 

 very unequal, narrow, united behind ; foot cylindrical elongated. 



Distribution, 4 species. Eiver Senegal. The marine species 

 are Diplodontce. 



Fossil, 1 species. Europe. 



Family XIII. — Cypeinidj]:. 



Shell regular, equivalve, oval or elongated ; valves close, 

 solid ; epidermis thick and dark ; ligament external, conspicu- 

 ous ; cardinal teeth 1 — 3 in each valve, and usually a posterior 

 lateral tooth ; pedal scars close to, or confluent with, the 

 adductors ; palUal line simple. 



Animal with the mantle-lobes united posteriorly by a curtain, 

 pierced with two siphonal orifices ; foot thick, tongue-shaped ; 

 gills 2 on each side, large, unequal, united behind, forming a 

 complete partition ; palpi moderate, lanceolate. 



One half the genera of this family are extinct, and the rest 

 (excepting Circe) were more abundant in former periods than at 

 the present time. CyjpHna and Astarte are boreal forms ; Circe 

 and Cardita abound in the Southern seas. 



Cyprina, Lamarck. 



Etymology, Kuprinos (from Kupris), related to Venus. 

 Type, C. Islandica, PI. XIX., Fig. 22. 



* Associated with the bones of Elephas meridionaiu. Rhinoceros leptorhUus, 

 Mastodcni Arvemensis, Hippopotamus major, ^c. 



