64 OF THE DONAX. GENUS IX. 



as Triinculus, cuneata, &c. ; but sunk in a groove in others, 

 as D. scripta, &c. 



The animal is a Cockle, and, like the Tellina and Venus, 

 protrudes two short tubes from the longer or pointed end, and 

 a short scythe-shaped foot from the front near the lower or 

 truncated end. 



The D. Irus is an exception, the animal being an Ascidia 

 (see Mont. Brit. Test. p. 573), with the teeth of the shell like 

 a Venus. 



Linnaeus describes 10 species, Gmelin has added 9, and 

 Dr. Turton none. Total, 1 9. 



The lines or grooves from the beaks to the margin are called 

 longitudinal strice ; but when marked with strokes in that 

 direction, but of a colour difterent from the rest of the surface, 

 they are said to be radiate Qpl. 2. f. 23). 



They are said to be transvei'sely striate when they have 

 lines or grooves parallel to the margin ; but when they are 

 marked with lines of another colour in tliis direction, they 

 are said to be banded. 



Lamarck divides this genus into two, as follows : 

 Petricola. Shell transverse and inequilateral, gaping a little 

 at both ends, having two muscular impressions, with two 

 hinge teeth on one valve and a bifid one on the other ; 

 cartilage external (Donax Irus. See pi. 2. /. 22). 

 Don AX. Shell transverse, inequilateral; cartilage external; 

 the hinge teeth two on the left valve ; lateral teeth one or 

 two on each valve, rather distant (Donax cuneata. See 

 pi. 2. f. 23). 



