88 



The valves are more or less pearly within, as are also 

 those of the Trigoniae, and evidently indicate an alli- 

 ance with the Naiades. LaMarck has not thought it 

 necessary to make a separate genus of those which 

 have the margins entire. 



Nucula lanceolata Nucula Nicobarica 



rostrata obliqua 



pella margaritacea. 



[Four fossil species.] 



TRIGONIA. 



/inn. du Mns. 4, p. 355, pi. 67,/ 2. 



The only recent example of this shell known to La- 

 Marck is the Trigonia margaritacea, a shell brought 

 from King's Island, New Holland, by Peron. The ge- 

 neric description of this shell allies it in some degree 

 to the Cardia and Cardita, but more particularly con- 

 nects it with the G. Castalia. From the locality of the 

 fossil species it is supposed to inhabit the sea in very 

 deep places. Shell equivalve, inequilateral, subtrian- 

 gular, sometimes suborbicular; cardinal teeth oblong, 

 flattened at the sides, divergent, and grooved trans- 

 versely; of which two on the right valve are grooved 





