MYA. 219 



alata, sliell moderately thick, subtriangular, gen- 

 erally gaping at the back part of the base, fus- 

 cous, wrinkled ; beaks near the back part, de- 

 corticated ; base straitish ; hinge- margin ob- 

 lique with a winged process ; red-purple with- 

 in ; teeth crenate. Dimensions five inches and 

 a half by three and three fourths. 



cylindrica, shell very thick, subcylindric, emargi- 

 nate forward ; pale horn-coloured and greenish; 

 hinge-margin undulated obliquely across the 

 wrinkles ; rough on each side ; beaks broad 

 and prominent ; pearly within ; teeth thick and 

 crenate ; cavity of the beaks very deep. Di- 

 mensions three inches and a quarter by one and 

 a quarter. 



undulata, shell subrhombic, with undulations, which 

 radiate from the beaks ; shell thick, obtusely 

 rounded behind ; hinge -margin somewhat wing- 

 ed ; epidermis blackish. 



plicata, shell subquadrangular, tumid, sinuous 

 before with distant oblique folds ; hinge-mar- 

 gin elevated, compressed, keeled ; shell thick* 



n-ndata, shell sub triangular, very tumid, undu- 

 lated ; lateral teeth two in each valve ; shell 

 thick, beaks projecting backwards ; epidermis 

 horn-colour approaching yellowish-green ; teeth 

 deeply furrowed and crenate, lateral teeth two 

 in each valve. 



clliptica, regularly oval, thick, convex, glabrous ; 

 beaks depressed ; teeth elevated, triangular, 

 striated ; shell long before and short behind ; 

 epidermis yellowish- brown, obscurely rayed ; 

 teeth deeply divided, finely striated ; pedrly 

 white, iridescent or flesh-colour within. Di- 

 mensions about four inches by two and a half. 



