98 



POPULAR CONCHOLOGY. 



oblong, transversely furrowed, two in the right 

 valve and four in the other; equivalve, inequi- 

 lateral, triangular, ribbed or furrowed, liga- 

 ment external. Animal, foot sharp. — 1 spe- 

 cies recent, 17 fossil. 



There is only one species, which is found in 

 the deep seas of New Holland. The interior 

 is lined with highly iridescent mother of 

 pearl. 



Lamarck had originally placed this genus 

 amongst the Arcacees (where Deshayes thinks it 

 should be placed) ; he afterwards made it, with 

 another genus Castalia, into a family ; but it has 

 since been ascertained that the Castalia belongs 

 to the UnionidcB, and it is therefore here left as 

 was originally intended. 



Family 1 1 . —Naiidcz. * 

 In this family there are four genera : they 

 are all inhabitants of fresh water, and particu- 

 larly of American rivers, of a dark brown co- 

 lour outside, caused by an epidermis, and very 

 pearly within, with teeth not very distinctly 

 visible. 



* Les Nayades, Lamarck. 



