BIVALVES. 49 
sharp at one end, and terminating in a point, by the 
aid of which, a hole is dug; it then alternately 
assumes the shape of a hook, and the spade already 
mentioned; one serving the purpose of shovelling 
out the sand, the other to assist the wary animal in 
his precipitous descent. When the Solen wishes to 
change his place of abode, the leg is again put in 
requisition; it then takes the shape of a ball, and 
is stretched as wide as possible. This ball prevents 
the creature from slipping back, while the reaction of 
the muscles throws him forwards. 
He has also a mantle in front, a curtain before the 
opening of his cell, which enables him to exclude the 
rough beating of the tide; and, moreover, he is 
furnished with two united breathing tubes, about 
three or four inches in length, from the upper end of 
the shell; and these he projects through the soft sand, 
for the evident purpose of maintaining a constant 
communication with the water. 
Without these admirable appendages, the Solen 
would be the most helpless of all shell-fish. He 
can neither moor himself to the nearest rock, like his 
relative, the Oyster, nor can he run upon his feet, 
nor raise himself from off the ground. These in- 
abilities are made up to him by the mantle, and the 
breathing tubes, and above all, by the cylindrical leg, 
which enables him to bore into the sand. In each of 
E 
