MOLLUSCA. 469 



qualified to act as suckers. The Limax tergipcs of 

 KAEL, Des. An. p. 99, is the type of the genus. T. rao- 

 culata, described by MONTAGU, Lin. Trans, vii. p. 80, 

 t. vii. f. 8, 9, is a British example. 



34. TRITONIA. Branchiae destitute of basilar sheaths. 

 The branchiae are in the form of plumes, or imbricated 

 productions, placed in a row on each side the back. The 

 tentacula, which are partially retractile, have a sheath at 

 Jie base. In some of the species there are indications of 

 eyes. 



The mouth consists of two lips, which are placed 

 longitudinally, 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 up- 

 per margin, for the purpose of cutting. Within these 

 is the tongue, which differs remarkably from the same 

 member in the Doris. In the latter, 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 func- 

 tions 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 longitudinal 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 situate be- 

 hind, enveloping the stomach, and intimately united with 

 the ovarium. The organs of generation exhibit nothing 

 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 T. arbor es- 

 cens> pinnatijida, and bifida, arc examples of British spe- 

 cies. 



