BIVALVES— DONAX. ae 
DONAX.—WEDGE-SHELL. 
DESCRIPTION OF PLATE IX. 
Dw. I.—Fig. 1. D, scortum. 
Diy. Il.—Fig. 4. D.denticulata. Drv. I1].—Fig. 3. D. madagascariensis. 
Fig. 5. D. trunculus. Diy. [V.—Fig. 2. D. scripta. 
Fig. 6. D. elongata. Fig. 7. D. stultorum. 
Shell bivalve, with generally a crenulated margin, the frontal margin 
very obtuse; hinge with two teeth, anda single marginal one 
placed a little behind, rarely double or triple. 
THE principal characteristic of the Donax is deriv- 
ed from its form, which (throughout its twenty-four 
species) is similar to that of a wedge, being very broad 
and thick at one extremity, and gradually tapering to- 
wards the other. The margin, which is generally of a 
deep color, is almost invariably crenulated or beset 
with small contiguous teeth; and the frontal margin is 
generally very obtuse: the anterior slope not unfre- 
quently gapes, and has a ligament situated near the 
fissure, which prevents the two valves from sepa- 
rating, when the animal has occasion to open them. 
Some specimens of this genus, in their external ap- 
pearance, bear a strong resemblance to the species of the 
Venus; but the examination of the hinge will always 
determine to which of the genera the shell belongs. 
The Donax presents so great a diversity in external 
character, that it has occasioned the genus to be sepa- 
rated into five divisions. In the first, the species ex- 
hibit a rough and decussated surface, caused by crowd- 
