MOLLUSCA: 167 
foot is fleshy, and furnished with numerous muscular fila- 
ments, which unite, in the superior part of the cloak, to 
form a strong muscle, by which the body adheres to the 
shell. The action of this muscle brings the shell close to 
the surface to which the foot adheres, or removes it to a 
distance. The head is furnished with a large, fleshy snout, 
supporting at the base two pointed tentacula. The eyes 
are placed on a small elevation at the external base of the 
tentacula. A little way behind the head, and below the 
cloak, on the right side, are two apertures, being the anus 
and orifice of generation. The gills occupy the same po- 
sition as in the preceding genera. In some, the branchize 
form a complete circle; in others, the circle is interrupted 
anteriorly at the head. 
Within the trunk, the mouth is fortified by two cartila- 
ginous cheeks, which, at their union anteriorly, support the 
base of the tongue. This last is a most singular organ. It 
is longer than the whole body, narrow, and covered with 
three rows of short reflected spines, interrupted longitudin- 
ally and transversely. Its fixed end only can be exercised 
in deglutition, its free end being coiled up the abdomen. 
On the upper side of the mouth is a semicircular osseous 
plate, or upper jaw. The gullet is furnished with a dilat- 
able pharynx. The stomach is elliptical, with the cardia 
and pylorus at opposite extremities. The intestines are 
variously folded, and are several times longer than the body. 
The salivary glands are minute. The liver is intimately 
united with the stomach and intestines. The heart is situ- 
ate on the left side, in the anterior part of the body. The 
auricle receives the aérated blood from one vein when the 
circle of the gills is complete, and by two when interrupted. 
This auricle is placed on the anterior side of the heart. An 
