166 BIVALVES. 



long, it protrudes in search of its food, which 

 consists of insects ; these may be seen passing up 

 its transparent 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 DON AX* Plural, Donaces. 



WEDGE SHELL. 



Generic Character. Shell bivalve, equivalve, 

 inequilateral ; the form like a wedge, broad, thick, 

 obtuse at the anterior end, and gradually 

 narrowing and lessening at the posterior ; the 

 margin is often crenulate, and usually gaping ; 

 the hinge has two central teeth in each valve, 

 and one remote lateral one; the ligament is 

 external. 



OBSERVATIONS ON THE SHELL AND ITS 

 INHABITANT. 



The wedge-like form of the Donaces easily 

 distinguishes them. The derivation of the name 

 from fcovaf, (donax) an arrow, may have been 



* Plate VIII. figures 5, 6. 



