62 
room vm. shell, Emarginula, Fissurella, Pileopsis, Calyp- 
Nat. Hist, traea, Crepidula, and Ancylus. The Bullseana 
contain the Bulfea aperta (Bulla aperta. Lin.), 
and several species of the genus Bulla. Laplysia 
and Dolabella are the genera of the next family. 
The shell of the former is a small cartilaginous 
scutcheon, which adheres to the posterior part of 
the back of the animal; that of the latter is 
wholly internal. The genera of the family Li- 
macina are, Parmacella, an internal shell, very 
rarely met with; Limax (the Slug), whose shell, 
a small testaceous lamina, is contained in a fleshy 
or coriaceous scutcheon, attached to the fore part 
of the back of the animal;—Testacella, and Vi- 
trina. The shells of the two last genera are ex¬ 
ternal. 
Order 3. Trachelipoda. The family Coli- 
macea, contains the genus Helix, a part of the 
numerous species of which are in this compart¬ 
ment. 
Table 1 8 . Helix continued, together with 
the genera Caracolla, Anostoma, Helicina, Pupa, 
Clausilia, and Bulimus. 
Table 19. The four remaining genera of 
the Colimacea, viz. Achatina, Succinea, Au¬ 
ricula, and Cyclostoma. 
Table 20. The families Melaniana, Pe¬ 
ristomata, and part of the Neritacea. The 
genera of the first are Melania, Melanopsis and 
Pirena: of the second, Valvata, Paludina and 
Ampullaria: 
