268 Dr. J. E. Gray on the Arrangement of 



being more ventricose, is said t have an animal like Buccinum, 

 and to live in the seas, — another example of the impossibility of 

 defining with accuracy and certainty, from the examination of 

 the shell alone, the genus, family, or even order to which a 

 Mollusk may belong. 



2. STREPTAXiDiE. The tentacle cylindrical, bifid, as if it 

 were the tentacle and the labial tentacle united. Shell subglo- 

 bose ; the large whorls excentric, flattened. Peristome thickened. 

 Carnivorous ; eating other Slugs and Mollusca. Streptaxis, 



** The spiral part of the body on the hinder part of the back. 

 Back and head with two or four lateral grooves from the front 

 of the mantle to the side of the head, including the eye-peduncle 

 and tentacles. 



3. Testacellad^e, Catal. p. 9. Testacella and Daudebardia. 

 Eating worms. 



Sect. 2. Phyllovora. The buccal mass small, ovoid, not pro- 

 duced. Jaw distinct, horny ; teeth numerous, four-sided, close 

 together on the lingual membrane. Herbivorous. 



* Mantle (either discal or spiral) defined, on the middle of the 

 back. Pulmonary cavity under the mantle, and attached to it. 

 Head without any lateral grooves, 



4. Helicid^e. Foot tapering behind, without any subcaudal 

 gland. Adult and young alike. (See Tribes in Catalogue, 

 p. 155.) 



I may observe that many of the genera referred by Mr. Adams 

 to the family Oleacinida have no affinity with it, and belong to 

 this family. 



5. ArionidjE. Tail with a distinct gland rather above the 

 foot. Adult and young alike. Arion, Geomalacus, &c. 



** Mantle convex, on the middle of the back of the animal. Pul- 

 monary cavity under the mantle, and attached to it. Head with 

 a central and two lateral diverging grooves enclosing the eye- 

 peduncles. 



6. ParmacelliDjE. Mantle central, large, shield-like, free in 

 front, more or less covered with a spiral shell. Young and 

 adult alike. Foot truncated behind, with a subterminal gland. 

 Parmacellus, Marietta, Laconia (Cat. pp. 62, 63), Vitrinella, 

 Nanina, and the allied genera will probably be found to belong 

 to this family when the animals are more closely ex amined 

 The genus Helicolimax (Cat. p. 181) differs from it in having no 



