35 1 
and boring marine animals. 
posed thus to travel, and indeed is generally to be found 
most readily by the furrow which it has ploughed up in its 
progress. In the summer it is met with on these shores in 
considerable numbers, above a furlong from low- water mark ; 
though at other seasons it is rarely seen, excepting after 
storms. Anodonta cygnaea offers an example of the same 
kind. It is thus, also, that Cyclas cornea crawls over a 
smooth surface, fixing itself by a viscid gluten, which exudes 
from the elongated foot in such quantity, that the animal in 
its progress leaves a silvery track like that of a snail. I 
have repeatedly seen small ones crawl up the side of a glass, 
and even support themselves on the surface of the water by 
a broad filament of this gluten extended from the side of the 
vessel. 
Although not habitually residing under the sand, the Buc- 
cinum undatum is entitled to a place among the burrowing 
marine animals. It is often found to have completely buried 
itself, apparently, for shelter ; and there are very strong 
reasons for suspecting that it habitually burrows in pursuit 
of its prey. 
As in the Bivalves inhabiting sand, its foot is the instru- 
ment of penetration ; and like them, it has the power of 
distending this organ to a size, nearly, if not quite equal to 
that of the shell. A section of the foot shows it to be 
divided into two nearly equal parts ; the powerful muscle, 
which extends from the operculum to the spire, forming the 
upper, or posterior half, and a cellular spongy mass consti- 
tuting the remainder. The lower surface of this portion is 
the disc on which the animal crawls ; and being considerably 
longer than the muscle, it is folded upon itself, when retracted 
