the Land Pulmoniferous Mollusca into Families, 269 



subcaudal gland, and a deep central dorsal posterior groove; 

 this may be the type of another family. 



So great is the difficulty of procuring the animals of exotic 

 land-shells for examination, that we can make only very gradual 

 attempts at revising the arrangement of them ; and great caution 

 becomes necessary, since we find that shells similar in external 

 appearance and character have animals of different conformation 

 and habits. 



7. Cryptellad^e. Mantle central, large, shield-like, free in 

 front. Young animal with an operculum, which is at length 

 deciduous, and protected by an external shell, which afterwards 

 becomes hidden in the shield-like mantle of the adult animal. 

 Jaw and teeth of Helix. Cryptella, Drusia, and Gerasia (Cat. 

 pp. 7 & 61). 



8. Aneitead^:. Mantle small, inequilateral, flat, sunken, 

 enclosing a shelly plate. Back with a central groove, giving 

 out opposite branches to the sides. Neck with two distinct 

 diverging grooves to the lips. Jaw horny; teeth square. 

 Aneitea. 



9. JANELLADiE. Mantle very small, convex, sunken in the dorsal 

 grooves, enclosing four small plates. Back with a single central 

 dorsal groove. Neck with two grooves, parallel and close to- 

 gether behind, and then separating and extending to the out- 

 side of the eye-peduncle. Skin spinulose. Tongue very broad. 

 Teeth oblique, strongly dentated. Janella. 



***Mantle covering the whole of the back. Respiratory chamber 

 small, thin, in the front of the body, separate from the mantle. 

 Head without any groove. Eye-peduncle and tentacle distinct. 

 Jaw and tongue like Helix. 



10. Philomycenim. Philomycus and Meghimatium. (See 

 Cat. p. 156.) 



B. Head, eye-peduncle, and tentacles simple, contractile. Teeth 

 numerous, four-sided, close on the lingual membrane. 



11. Vermicellim. Body elongate. Tentacle bifid. (See 

 Cat. p. 4.) 



12. Onchidiad^e. Body ovate. Tentacles cylindrical, simple. 

 (See Cat. p. 4.) 



