MOLLUSC A , 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 branchiae 

 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 aerated 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 



