BIVALVES. m<v<:;tra, 39 



*Solida — Strong. Glauca — Red-rayed. 



♦Lutraria — Large. Pellucida — Pellucid. 



Cygnus — Swan. Fragilis — Brittle. 



Maculata — Spotted. Rugosa — Rugged. 



Turgida — Inflated. Nicobarica — Nicobar. 



Violacea — Violet. Complanata — Flat. 



Cuneata — Wedge-shaped, * Listen — Lister's. 



Piperata — Pepper. 



DONAX. — Wedge-shell. 



Animal — a Tethys: Shell hivalve^ with generally a crenu- 

 late margin^ the frontal margin is very obtuse; hinge 

 with two teethf and a single marginal one placed a little 

 behind, rarely double or triple. 



The most leading characteristic of the Donax is derived 

 from its form, which (throughout the nineteen species) is 

 similar to that of a wedge, being very broad and thick at 

 one extremity, and gradually narrowing and lessening to 

 the other. The frontal margin is generally very obtuse, 

 and the anterior slope is not unfrequently furnished with 

 a sort of fissure or gape ; near to which is situated a car- 

 tilaginous ligature or ligament, which prevents the two 

 shells from separating when the animal has occasion to 

 open them. 



Some of this genus, however, are a little ambiguous 

 in their external appearance; so much so, that they fre- 

 quently create a doubt whether they should not be rank- 

 ed among the species of the Venus ; but in these cases the 



