PNEUMONOBKANCHIATA. 
49 
phragm formed of its inspissated humours^ and some- 
times hardened with a little calcareous matter. 
These animals are all hermaphrodite^ but require 
mutual impregnation^ and feed on vegetables; but 
some few have carnivorous propensities^ and others, 
when they live near man, acquire bad habits, and 
eat paper and dead animal matter. 
They may be divided into groups, according to 
the structure of the mouth, and the form of their 
tentacles, which conform to their more or less aquatic 
habits. 
This order is divided into four sub-orders, in the 
following manner : — ■ 
I. Peteophila. — Eyes at the end of an elongated 
contractile peduncle ; tentacles flat, contractile ; 
jaws none; organs of generation far apart, 
apertures united by a lateral groove ; teeth flat, 
four-sided, close, side by side; shell none, as 
OnchidiadcE. 
II. Geophila. — Eyes at the end of an elongated 
retractile peduncle ; tentacle cylindrical, re- 
tractile, sometimes wanting; organs of gene- 
ration in a common cavity ; operculum none. 
Terrestrial. 
1. Lumbricivora. — Mouth proboscis-like; jaws 
none; teeth slender, conical, distant. Carni- 
vorous, subterraneous, as TestacellidcB, 
2. Phyllivora . — Mouth prominent; jaws one or 
two, distinct ; teeth four-sided, flat, with a re- 
curved tip, close together, side by side; her- 
bivorous, as Arionidce and HelicidcB. 
E 
