162 BIVALVES. 



ated; umbones small, central; hinge without 

 lateral teeth, cartilage cavity large, triangular, 

 cardinal teeth small, a single one locking into a 

 bifid one in the opposite valve ; of a yellowish, 

 reddish, or white colour often stained with black 

 occasioned by the mud in which it resides ; about 

 an inch and quarter long, and an inch and half 

 broad. 



This is one of the most beautiful of the British 

 species of Mactra; it is chiefly found at the 

 mouth of inlets or rivers, not remote from fresh 

 water ; for though it always seeks a spot within 

 reach of the flux of the tide, it delights in situa- 

 tions over which fresh water occasionally flows. 

 It lives in the mud, buried about five or six inches 

 deep. The animal has two slender tubes of a 

 yellowish colour placed near together at the an- 

 terior end : one about three inches long it pro- 

 trudes in search of its food, which consists of in- 

 sects ; these may be seen passing up its trans- 

 parent siphon, drawn in with the current of water 

 it is continually receiving, and which it discharges 

 at the shorter tube, retaining only the nutritious 

 matter it contained. 



GENUS. DONAX.* 



WEDGE SHELL. 



Generic character. Shell bivalve, equivalve, 

 inequilateral ; the form like a wedge, broad, 



* Plate VIII. figures 5, 6. 



