PLEUROBRANCHUS. APLYSIA. 



t 



. SO.-PLEUROBRANCHUS. 



are composed of leaflets, 

 more or less divided, at- 

 tached along the right side 

 (fig. 80, br), or on the 

 back (fig. 81), and more 

 or less covered by the 

 mantle, which almost al- 

 ways encloses a small 

 shell in its thickness. 

 Their form is very variable. They are divided into Pleurobran- 

 chus, Pleurobranchides, Aplysia, Dolabella, Akera, &c. 



37. The PLEUROBRANCHI are mol- 

 lusks of an oval form ; in which the 



t branchiae are fixed on the right side, 

 between the mantle and foot (Jig. 80). 

 y The mouth is in the form of a proboscis 

 t or trunk, and is surmounted by a small 

 triangular veil, and two tentacles; they 

 have four stomachs, the second one of 

 which is sometimes armed with bony 

 pieces, and the anus opens behind the 

 branchise. One species, of a lemon 

 yellow colour, is found on the coasts of 

 France. 



38. The APLYSUE, which the ancients 

 called sea-hares, have a very singular 

 form ; the body resembles that of a 

 sort of Limax ; but the edges of the 

 foot, erected in flexible crests, surround 

 the back and may be even reflected over 

 it. Their head is supported by a neck 

 of greater or less length, and furnished 

 with four tentacles (fig. 81, f), the two 

 upper ones being hollowed like the ears 

 of a quadruped, and placed above the 



eyes (y). The branchiae, in the form of very complicated 



Fig. 81. APLYSIA. 



Explanation of Fig. 80. m. the mantle, raised up to show the branchiae, 

 br ; a. the anus ; b. the mouth and trunk ; v. the veil ; t. the tentacles ; 

 p. the foot. 



Explanation of Fig. 81. , t. the tentacles ; y. the eyes ; m. the mantle ; 

 b. the branchice. 



37. What are the characters of the genus Pleu'robranchus ? (Pleuro- 

 branchus, from the Greek, pleura, side, and bragchia, gills.) 



38. What are the characters of the genus Ap/y'sia? (Aplysia, from 

 the Greek, aplusia, uncleanness.) 



