GASTEROPODA PULMONEA. 



347 



The Pectixibranchiata 

 Have the sexes separated ; their respiratory organs consist aUnost ahva3's ot oranchia; composed 

 of hmiellae united in a jiectinated form, and ivliich are concealed in a dorsal cavity opening '.vith 

 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 SCUTIBRANOHIATA 



Have branchi;c similar to those of the Pectiuibranchiata, but they are comi)lete hermaphrodites, 

 ami require no union with a seeond to effect impregnation ; their shells arc very open, and in 

 several like a shield; they never have any operculum. 



The Cvclobranciiiata 

 Are herma[)hrodites of the same kind as the Scutibranchiata, and have a shell consisting of 

 one or several ]iieces, hut in no case turbinate nor operculate : their brauchi;e lie under the 

 margin of their cloak, as in the Inferobrancliiata. 



THE FIRST ORDER OF GASTEROPODES. 



THE PULMONEA.* 



From other MoUusca, 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 

 dihite or contract at pleasure. They have, also, no braucliia;, but only a network of |ndmonary 

 vessels, which creep upon the ^^ alls, and more particularly upon the ceiling of their respiratory 

 cavitv. Some of them are terrestrious, and others live in the water, liut these are necessitated 

 to come, from time to time, to the surface, to receive \\'ithin their pulmonary cavity the air tit 

 for respiration. All of them .are hermaphrodites. 



The Terrestrial Pulmonea have almost all four tentacula, for, in a few only, of s na 1 

 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 Linna;us which is diridcd as fohows : — Tlie Limaces, properly so called (Zimar, Lam.), have an 

 elongated bodv, 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, 

 Hat shell or at least, in lieu of it, a calcareous [molecular] deposition. The respiratory orifice is at tlie 

 ri^ht siile of the shield, and the anus opens near it. The four tentacula are protruded and withdrawn 

 hv a process of evolution and involution ; and the head itself can he contracted partially under the disk 

 of the cloak. The orifice of the generative organs is under the right superior tentaculuin. In the moutli 

 is an uiincr jaw only, of a crescent form, and toothed, which enables them to devour with voracity herlis 

 ani fruits to which thcv arc vcrv destructive. Their stomach is elongated, simple, and membranous. 



JM. de Ferussac distinguishes tlie Arions by the 

 respiratory orifice being; towards the anterior part of 

 the shield, in ^vliich tiiere are only calcareous granules. 

 L/max nifiiSy Linn., is an example which we meet 

 A\ith every step in moist seasons, and which is some- 

 times almost wholly black. It is the species of whicli 

 ;i broth is used in diseases of the chest. The Lunax 

 proper, has the orifice near the hinder part of the 

 shield, and it contains a more distinctly formed shell 

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



l„ yf BUiiiville. [In coiist-q.ie 

 , pulmi,,„iicd bcint' upjiliLd to J 



\t. 



i,m-k, Ell 

 -Eu.] 



[i=li uulhuri often call tliis cnlci 



