GASTEROPODA PULMONEA. 347 



The Pectinibranchiata 

 Have the sexes separated : their respiratory organs consist almost always ot oranchi;e composed 

 of lamella; united in a pectinated form, and which arc concealed in a dorsal cavity opening w it li 

 a wide gape ahove 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 Scutibkanchiata 



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 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 winch 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 tit 

 for respiration. All of them are hermaphrodites. 



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

 size, we cannot sec the inferior pair, probably because of their littleness. 

 Tbose of them which have no apparent shell, form the genus 



Limax — 

 Of Linnaeus, which is divided as follows : — The Limaces, properly so called {Limax, Lain.), have an 

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

 pari of the back, and covers only the pulmonary sac. It contains, in several species, a small, oblmiL', 

 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 arc 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 Buperior tentaculum. In the mouth 

 i- a ■: 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, anil membranous. 



M. de Perussac distinguishes the ArUnu bj the 

 respirator) orifice being towards the anterior pa 

 the shield, in which there areonly calcareous granules, 

 Limai rufiis, I. inn., i> mi example which »i meet 

 wiili ever] step in moist seasons, and which lasom*. 

 times almost wholly black. It is the species of which 

 ;< broth i~ used in <ii^> -ice- ol thei best i 

 proper, has the orifice near the binder part of the 



r -Una run.,. shield, and il contains a i e distinct!] formed shell 



Such are the JUmuu mari»m* and /...; Unn. 



• '■ BUlnvillr. (In coDMqacnc* <.f »..mr nh- I ulrsali, vrgti bj Uunrck, SngUih nlhan often call ibl. order the 



• to lot torn !'•■'■• H •pplM la »ny Innrttbimlad ' Pntumon tu] 



