DONAX WEDGE SHELL. 167 



adopted either as indicative of the sagittate 

 form, or of the rapidity with which, in conse- 

 quence of its peculiar shape, the animal can 

 dart into the sand, whenever danger threatens. 

 One species (Donax Irus) perforates the hardest 

 limestone, but by what means it effects a lodg- 

 ment in such a substance, has not been ascer- 

 tained ; pieces of stone are often thrown ashore 

 on the Devonshire coast filled with these shells 

 fitting into the apertures which they have pierced. 

 The shells of this genus are generally of a fine 

 rich purple colour, sometimes marked with rays 

 of purple on a white ground. Many of the 

 species are of a yellow olive hue. The animal 

 has two long slender tubes not joined together, 

 and a lamellar foot. The Donaces are marine 

 littoral shells. 



DONAX Denticulate. \ ,., 



TOOTHED DONAX. 



Specific Character. Shell strong, thick, ovate, 

 wedge-shaped, with longitudinal striae, the in- 

 terstices punctured ; * anterior slope rough, with 

 transverse striae, and elevated in the middle in 

 a kind of keel ; white or lead colour, usually 

 with a few purple rays proceeding from the 

 urabones, inside purple ; very concave under 



* Punctured, pricked or marked with small dots, from the 

 Latin punctww, a point or dot. . v " - 



