38 BIVALVES DON AX. 



ed striae, crossing each other in a transverse and longi- 

 tudinal direction, thus giving the shell a spiny appear- 

 ance, as in the D. scortum and D. pubescens. The 

 second and third divisions are also characterized by the 

 position of the stiiee, which in the one are longitudinal, 

 and in the other transverse. The shells of the fourth 

 division have a smooth and polished surface ; and the 

 fifth at present consists of one species only, which has 

 its surface partially covered with transverse membrana- 

 ceous ridges. 



The most prevailing color is a rich purple, which 

 sometimes only appears in rays on a white ground, di- 

 verging from the beaks to the margin. Many of the 

 species are of an olive-yellow tinge, which often in- 

 clines to a bright orange ; and others, again, have a 

 pink hue, finely diversified with brown zigzag mark- 

 ings, as in the D. scripta, &c. and in some instances the 

 shells are variously banded. The interior almost al- 

 ways partakes of the coloring of the exterior. 



It is doubtful whether any shells of this genus are 

 natives of rivers, as they are generally found buried 

 in the sand of the sea shore. Although the species 

 and varieties are but few, and thinly scattered over 

 most parts of the globe, yet some coasts (the European 

 in particular) supply a profusion, but of no great 

 variety. 



The Donax derives its name from its shape, which 

 resembles the barbed head of a javelin or dart (^6va^). 



