GASTEROPODA PULMONEA. 



347 



The Pectixibranchiata 

 Have the sexes separated : their respiratory organs consist almost always ot oranchise composed 

 of lamellae miited in a pectinated form, and wliich 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 are 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 consistinc of 

 one or several ]ueces, 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 PULMOXEA.* 



From other MoUusca, those of this oi-der 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 Linnaeus, which is divided as follows : — The Limaces, properly so called {Limax, Lam.), have an 

 elongated body, and a closely-fitted fleshy disk, or shield, for a cloak, which occupies merely the anterior 

 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 

 l)y 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 voracitv herbs 

 and fruits, to which tliey are very destructive. Their stomach is elongated, simple, and membranous. 



M. de Ferussac distiiii^uishes the Arions by tlie 

 respiratory orifice being towards the anterior part of 

 the shield, in wliicli there are only calcareous graivulcs. 

 Limax riifus, 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 

 !i broth is used in diseases of the chest. The Umax 

 proper, has the orifice near the hinder part of tlie 

 shield, and it contains a more distinctly formed shell 

 Such are the Limax maximus and L. agrestris of Linn. 



• f'ulmobmnc/iialu of Blai.iville. [In consequence of sr 

 jeclions tu the term puhiiuaaud beint' apiilied to any inver 



, uracil by Lamarck, English authors 

 ntnbraudivus. — Ku.j 



)(ten call this order the 



