Order 1. GASTEROPODA PULMONEa. 339 



The Pectinibranchiata 

 Have the sexes separated : tlieir respiratory organs consist almost always of brancliia; composed 

 of lamellcE 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 eraarginate, 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 branchise similar to those of the Pectinibranchiata, but they are complete hermaphrodites, 



and require no union with a second to eflFect impregnation : their shells ai'e 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 : tlieir branchiae lie under the 

 margin of their cloak, as in the Inferobranchiata. 



THE FIRST ORDEH 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 jiulmonary 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 appai-ent 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 Ueu of it, a calcareous [molecular] deposition. The respiratory orifice is at tlie 

 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 ir under the right superior tentaculum. In the inoutli 

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

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



M. de Ferussac distinguishes the Arions by the 

 respiratory orifice being- towards the anterior part of 

 the shield, in which there are only calcareous g-rar,u!es. 

 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 aear the hinder part of the 

 Fig. 157 —Limax rufus. shield, and it contains a more distinctly formed shell 



Such are the Limax ma-ximus and L. agrestris of Linn. 



* Fmmoliranchiala of Blainville. [In consequence of some ob- I animait, nr^ed by Lamarck, English authurs often call this order tlit 

 jectionii to the leiin pulmunated being applied to any invcrtebrated .' Pneufnounbraiichous.—i^u.i 



