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 PiaTE 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 Tellinidze, 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 (Linnzus). 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 Dovax is nearly triangular in shape, com- 
pressed, longer than broad, regular, equivalve, not equilateral ; the 
hinge with three or four teeth on each valve. 
The animal is slightly compressed, and more or less triangular. 
