SUNETTA. 



427 



Ex. T. tripla, Linnceus, pi. 108, fig. 2, 2, . 



The shells in this genus are usually thin, gihhous, and 

 triangular, the heaks are very prominent, the lunule is 

 indistinct, the internal margin of the valves is entire, and 

 the hind cardinal tooth of the hinge is torn and divided. 

 There are ahout twenty-nine species described, from the 

 West Indies, the Mediterranean, Senegal, the Cape, India, 

 and Western America. Fossil species occur in the Miocene 

 of Bordeaux. 



Species of Tivela. 



gequilatera, Desk. 

 ambigua, Desk. 

 argentiua, Sow. 

 bicolor, Gray. 

 compressa, Sow. 

 crassatelloides, Conr. 

 damaoides, Gray. 

 Dillwynii, Desk. 

 dolabella, Sow. 

 fulrninata, Phil. 

 gracilior, Sow. 

 Hanleyana, Soiv. 

 Hindsii, Hartley. 

 humilis, Cpr. 

 incerta, Sow. 



intermedia, Sow. 



laevigata, Gray. 



lineata, Sow. 



mactroides, Born. 



nitidula, Lam. 



planulata, Brod. and Sow. 



polita, Sow. 



radiata, Soiv. 



stultorum, Gray. 



trigonella, Lam. 



tripla, Linn. 



undulata, Sow. 



ventricosa, Gray. 



virginea, Adams and Reeve. 



Genus SUNETTA, Link. 



Shell ovately trigonal, sub-equilateral, compressed, pos- 

 terior side the shortest; lunule lanceolate, the area deeply 

 excavated ; margins thin and regularly denticulate. Hinge 

 narrow, bi-dentate in one valve, tri-dentate in the other; 

 anterior lateral tooth narrow, affixed to the hinge-margin. 



