64 CLASS III. GASTEROPODA. ORDER VI. PULMOBRANCHIATA. 
Family 2. COLIMACEA. 
Testa spirivalvis, aut turriculata, aut globosa, aut discoidea, apertura in- 
tegra, labro vel simplici vel reflexo ; operculo nullo, sed apertura 
interdum munimento duro, temporario, epiphragma dicto, inclusa. 
The family of the Colimacea or Snails commences that portion of the 
gasteropodous mollusks which Lamarck distinguished by the title of Tra- 
chelipoda. They were called trachelipodous, or neck-moving, because 
he considered the expanded disc or foot by which they acquire motion 
to be cervical, attached to the neck, the body being of a spiral form, 
enclosed within a spiral shell, moulded thereon, from which it cannot 
depart. The transition, however, as we have shown in our observations 
on the preceding genus, from the limaciform to the heliciform type, is so 
gradual and complete, that it is quite impossible to say where the one 
finishes, or the other begins; the animals of both are moreover closely 
allied by the similarity of their breathing apparatus. De Blainville 
does not even regard them as separate families ; for in his ‘ Manuel de 
Malacologie’ we find the Colimacea included in his family of the Li- 
macinea. 
The land mollusks, being naturally the first to attract the attention of 
naturalists, appear to have received the common appellation of snails, 
without reference to their many varieties of form or structure. Linnzus, 
indeed, was perhaps less judicious than many of his predecessors, for in 
his genus Helix he included many fluviatile and marine species as well 
as terrestrial. Bruguiére commenced a reformation in the Linnean 
Helices by separating the elongate varieties under the new title of Buli- 
mus, and it was in a manner completed by Lamarck by the formation 
of the genera Achatina, Pupa, Cyclostoma, Lymnea, Melania, Auricula, 
Ampullaria, &c. Lamarck’s method is still indeed the most legitimate 
