PLEUROBRANCHUS.— APLYSIA. 



63 



are composed of leaflets, 

 more or less divided, at- 

 tached along the right side 

 {jig. 80, hr)^ or on the 

 back (Jig. 81), and more 

 or less covered by the 

 mantle, which almost al- 

 ways encloses a small „. o^ 



,-'.,. . , . , Fiff. 80. PLKUROBRANCHUS. 



shell in Us thickness. — 



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



chusy Pleurohranchides, Aplysia, Dolabella^ Akera, &c. 



37. The Pleurobrajvchi are mol- 



lusks of an oval form ; in which the 



t branchite are fixed on the right side, 



between the mantle and foot {fig. 80). 



y The mouth is in the form of a proboscis 



i 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 



branchife. One species, of a lemon 



yellow colour, is found on the coasts of 



■m France. 



jj 88. The Aplysi-^, 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 (fg. 81, t), 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 branchioB, 

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

 — p. the foot. 



Explanation of Fig. 81. — t, t. the tentacles ; — y. th5 eyes ; — w. the mantle ; 

 — 6. 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 Aplasia? (Aplysia, from 

 the Greek, aplusia, uncleanness.) 



