LUTRARIA. 383 



Genus EASTONIA, Gray. 



Shell oblong, rather ventricose, thick, equilateral, radi- 

 ately ribbed ; hinder slope rugose ; hinder gape small. 

 Hinge with the cardinal teeth of the left valve compressed, 

 notched ; anterior lateral tooth nearly perpendicular ; liga- 

 ment sub-external, marginal, not separated from the car- 

 tilage. 



Ex. E. rugosa, Gmelin, pi. 101, fig. 4, 4, a. 



The only species of Eastonia known is from the coast of 

 Guinea, and is characterised by its ventricose form, and the 

 radiately ribbed surface of the valves. 



Genus LUTRARIA, Lamarck. 



Shell oblong, elongate, rather compressed, sub -equilateral ; 

 umbo sub-anterior; hinder gape moderate, or large. Hinge 

 with the cardinal teeth distinct; anterior lateral teeth erect, 

 hinder very small, often obliterated in adult shells ; liga- 

 ment sub-external, marginal, not separated from the car- 

 tilage. 



Syn. Cacophona, Gist. Cultellus, Sow., not 8 chum, or 

 Conrad. Lutaria, Phil. Psammophila, Leach. 



Ex. L. oblonga, Gmelin, pi. 101, fig. 5. Shell, L. 

 elliptica, Lamarck, fig. 5, a, 5, b. 



The species of Lutraria are found on the shores of 

 various countries living buried vertically in the sand or 

 mud, especially of estuaries, at depths ranging from low- 

 water to twenty fathoms. They are from temperate cli- 

 mates; Australia, the Philippines, New Zealand, Britain, 



