ANATOMY AND PHYSIOLOGY OF A SNAIL. 2/ 



concave interiorly. In a third case, Bulla lignaria, there are 

 three plates, attached to which are strong muscles, but these 

 plates are calcareous, and not horny, as are those of Bullcea aperta. 

 It will be a reminder to those who are careless, to know that these 

 calcareous plates in the stomach of Bulla have been wrongly 

 described as a new bivalve shell, under the name of Gioenia. Our 



Fig. 8. Anatomy of H. Poinatict (after Cuvier). The mantle-cavity is opened on 

 the left side, and the mantle is turned over to the right. The body cavity has been 

 opened, and the viscera are unravelled. Cg, supra-cesophageal ganglion ; Sp, salivary 

 gland ; M, crop ; D, intestine ; Z-, " Mitteldarmdriise " (digestive gland, hepato- 

 pancreas, gland "of mid-intestine, liver) ; A, anus ; At, auricle ; C, ventricle ; PI, lung 

 Zd, hermaphrodite gland invested by lobes of the " Mitteldarmdriise" ; Ed, albumi 

 niparous gland ; Pr, prostate ; Ut, female portion of the common generative duct 

 Ks, receptaculurn seminis or spermatheca ; Dr, muciparous glands ; Ps, dart-sac 

 P, penis ; Fl, flagellum ; Mr, retractor muscle of the penis ; S#, spindle muscle. 



own fresh-water form, Limncea stagnalis, approaches the condition 

 of things, I think, found in Bullcsa aperta. It has a strong stomach, 

 and is in the habit of swallowing pebbles from the bed of the 

 pond, for the purpose, no doubt, of aiding in the trituration of its 



