i164 MOLLUSCA- 
Genus TritonrA.—Branchie destitute of basilar sheaths. 
The branchiz are in the form of plumes, or imbricated pro- 
ductions, placed in a row on each side the back. The ten- 
tacula, which are partially retractile, have a sheath at the 
base. In some of the species there are indications of eyes. 
The mouth consists of two lips, which are placed longitudi- 
nally, and open into a short canal. The jaws consist of two 
corneous plates, united at the upper dorsal edge, slightly 
arched, and meeting at their upper margin, for the purpose 
of cutting. Within these is the tongue, which differs re- 
markably from the same member in the doris. In the lat- 
ter, the spines with which it is beset are reflected, and draw 
the food to the gullet, while in the former, the spines are 
deflected, and serve to keep the food within the reach of . 
the jaws. The tongue of the doris, therefore, serves for 
deglutition, that of the tritonia for mastication. M. Cuvier 
describes the functions of both as similar. The salivary 
glands are placed on each side the gullet, and empty their 
contents behind the jaws. The gullet has a few longitudi- 
nal folds; the stomach is simple, scarcely differing from the 
gullet ; and the intestine proceeds almost directly to the 
anus, situate on the right side. The liver is small, and situ- 
ate behind, enveloping the stomach, and intimately united 
with the ovarium. The organs of generation exhibit no- 
thing remarkable. The pedunculated vesicle has a simple 
canal. The external opening of the organs of generation 
is situate a little before and beneath the anus. The 7. 
Hombergii arborescens, pinnatifida, and bifida, are exam- 
ples of British species. 
Genus ScyLtEA.—Branchie seated dorsally on the fins. 
Tentacula two. On each side of the back are two mem- 
branaceous expansions, and one on the tail, supporting on 
