334 THE OCEAN WORLD. 



gaping and truncated at both extremities. The tints are rose-coloured, 

 bluish-grey, and violet; the valves are generally covered with an 

 epidermis of a greenish brown. 



The animal which lives in this elegant dwelling has the form of 

 an elongated cylinder. Its mantle is closed in its whole length, and 

 only open at the ends at one side for the passage of the food to the 

 mouth, and at the other for the passage of a tube formed of the two 

 siphons united together. This curious shell, various species of which 

 are presented in PLATE XII., is known as razor-fish, sabre-fish, and 

 other names, which in some respects indicate the peculiar form and 

 appearance of the shell. 



The Tellinidae, the sixth family in our table, is very important, as 

 including a vast number of genera and species, of which, as types, we 





Fig. 135. Donax rugosus (Linnaeus,). Fig. 136. Donax denticulatus. 



will particularise Tellina and Donax; but Galatea, Mesodesma, 

 Semele, Sanguinolaria, Psammobia, and Capsula, are also important 

 genera. 



Along the shores of the Channel and in the Mediterranean there 

 are few bivalves more abundant than the several species of the genus 

 Donax. They live near the shore in shallow water, burying them- 

 selves perpendicularly in the sand. They have the very singular 

 habit, considering their apparent helplessness, of being able to leap 

 to a certain height and then project themselves ten or twelve inches. 

 This may often be witnessed in the case of individuals left by the 

 retreating tide. If seized by the hand, and attempts are made to 

 disengage them from the sand, they continue to impress on their 

 shell a sudden and energetic movement, aided by the elasticity of 

 their foot, which is at once decisive and angular. 



The shell of the genus Donax is nearly triangular in shape, com- 

 pressed, longer than broad, regular, e'quivalve, not equilateral ; the 

 hinge with three or four teeth on each valve. 



The animal is slightly compressed, and more or less triangular. 



