GASTEROPODA PULMONEA. 
347 
The Pectinibranchiata 
Have the sexes separated : their respiratory organs consist almost always ot oranchise composed 
of lamellae united in a pectinated form, and which are concealed in a dorsal cavity opening with 
a wide gape above the head. Nearly all of them have turbinated shells, with the mouth 
sometimes entire, sometimes emarginate, sometimes produced into a syphonal canal, and gene- 
rally capable of being more or less exactly closed by an operculum attached to the foot of the 
animal behind. 
The Scutibranchiata 
Have branchiae similar to those of the Pectinibranchiata, but they are complete hermaphrodites, 
and require no union with a second to effect impregnation : their shells axe very open, and in 
several like a shield ; they never have any operculum. 
The Cyclobranchiata 
Are hermaphrodites of the same kind as the Scutibranchiata, and have a shell consisting of 
one or several pieces, but in no case turbinate nor operculate : their branchiae lie under the 
margin of their cloak, as in the Inferobranchiata. 
THE FIRST ORDER OF GASTEROPODES. 
THE PULMONEA.* 
From other Mollusca, those of this order are distinguished in this, — that they breathe the 
atmosphere through a hole which opens under the margin of their cloak, and which they can 
dilate or contract at pleasure. They have, also, no branchiae, but only a network of pulmonary 
vessels, which creep upon the walls, and more particularly upon the ceiling of their respiratory 
cavity. Some of them are terrestrious, and others live in the water, but these are necessitated 
to come, from time to time, to the surface, to receive within their pulmonary cavity the air fit 
for respiration. All of them are hermaphrodites. 
The Terrestrial Pulmonea have almost all four tentacula, for, in a few only, of small 
size, we cannot see the inferior pair, probably because of their littleness. 
Those of them which have no apparent shell, form the genus 
Limax — 
Of Linnseus, which is divided as follows : — The Limaces, properly so called {Limax, Lam.), have an 
j elongated body, and a closely-fitted fleshy disk, or shield, for a cloak, which occupies merely the anterior 
I part of the back, and covers only the pulmonary sac. It contains, in several species, a small, oblong, 
flat shell, or at least, in lieu of it, a calcareous [molecular] deposition. The respiratory orifice is at the 
right side of the shield, and the anus opens near it. The four tentacula are protruded and withdrawn 
by a process of evolution and involution ; and the head itself can be contracted partially under the disk 
of the cloak. The orifice of the generative organs is under the right superior tentaculum. In the mouth 
is an upper jaw only, of a crescent form, and toothed, which enables them to devour with voracity herbs 
and fruits, to wEich they are very destructive. Their stomach is elongated, simple, and membranous. 
Fig. 157 . — Limax rufus. 
M. de Ferussac distinguishes the Arions by the 
respiratory orifice being towards the anterior part of 
the shield, in which there are only calcareous granules. 
Limax rufus, Linn., is an example which we meet 
with every step in moist seasons, and which is some- 
times almost wholly black. It is the species of which 
a broth is used in diseases of the chest. The Limax 
proper, has the orifice near the hinder part of the 
shield, and it contains a more distinctly formed shell 
Such are the Limax maximus and L. agrestris of Linn. 
* Pulmobranehiata of Blainville. [In consequence of some ob- I animals, urged by Lamarck, English authors often call thi.s order the 
jections to the term pulmonated being applied to any invertebrated * Pneumonnbranchous . — Ed.] 
