GASTEROPODA PULMONEA. 329 



by respiring elastic air through a hole opening under the 

 margin of the mantle, and which they dilate and contract at 

 will; they have no branchiae, but a mere net-work of pulmo- 

 nary vessels which creep over the parietes of the respiratory 

 cavity and chiefly on its ceiling. 



Some of them are terrestrial ; others are aquatic, but are 

 compelled to visit the surface from time to time for the pur- 

 pose of opening the orifice of their pectoral cavity, or to re- 

 spire. They are all hermaphrodite. The 



PULMONEA TERRESTRIA 



Have generally four tentacula ; in two or three only, of a very 

 small size, the lower pair are not to be seen. 



Those which possess no apparent shell, form in the Linnaean 

 system the genus 



I LiMAX, Lin. 



Which we divide as follows: 



LiMAX, Lam. 



The body elongated, and the mantle, a dense fleshy disk which is 

 confined to the forepart of the back, merely covering the pulmonary 

 cavity; in several species it contains a small, flat and oblong shell, 

 or at least a calcareous concretion in place of it. The respiratory 

 orifice is on the right of this species of shield, and the anus on the 

 margin of that orifice. The four tentacula are protruded and re- 

 tracted, evolving themselves like the inverted fingers of a glove, and 

 the head itself can be partly withdrawn under the disk of the mantle. 

 The genital organs open under the upper right tentaculum. The 

 mouth has only an upper jaw, resembling a dentated crescent, which 

 enables these animals to gnaw fruits and herbs, which they do with 

 so much voracity as to eff*ect considerable injury. The stomach is 

 elongated, simple and membranous. 



M. de Ferussac distinguishes 



Arion, Fer., 



Where the respiratory orifice is towards the anterior part of the 

 shield, which merely contains a few calcareous granules. Such is 

 Limax nifus, L.; Ferussac, Moll. Terr, et Fluv., pi. 1 and iii. 

 It is everywhere to be met with in wet weather, and is some- 

 VoL. IL 2 R 



