70 



POPULAR CONCHOLOGY. 



land, Africa, and the European seas ; the 

 Indian species is rare, and very beautiful. 

 They are found generally in sands and shallow 

 water. 



21. Theacia (Leach). — Shell oval oblong, 

 sub-equilateral, in- 

 equivalve, a little 

 gaping at the ends; 

 hinge consists of a 

 more or less promi- 

 nent spoon-shaped 

 tooth in each valve 

 receiving the liga- 

 ment. Pallial impression deeply marked. Ani- 

 mal, mantle thick, foot rather small and com- 

 pressed. — 3 species, recent and fossil. 



These shells are thin, fragile, and generally 

 covered with an epidermis. They are found in 

 the Mediterranean Sea and on the coast of 

 Senegal. 



The two following genera Lamarck had 

 formed into a family and placed after his Mac- 

 tracees; but Deshayes and other authors place 

 them amongst the Myidce, as they agree in all 

 Accessary particulars. 



