GASTEREOPODA PULMONEA. 29 



ing the orifice of their pectoral cavity in order to respire. They are 

 all hermaphrodite. The 



PULMONEA TERRESTRIA 



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

 size, the lower jjair are not to be seen. 



Those which possess no apparent shell, form in the Linneean sys- 

 tem the genus 



LiMAX, Lin. 



Which we divide as follows : 



LoiAx, properly so called. Lam. 



Have the body elongated, and the mantle, a dense fleshy disk which 

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



Genus Melanla "j 



.... Melanopsis.. . . /• 



.... Pii-ena -' 



.... Valvata i 



, . . Paludina ? 



,. ., Ampullaria,. ,. J 



Vavicella ,, . . ~i 



Neritina I 



Nerita ...... j 



Natica } 



Janthina 



Sigaretus ►. 

 Stomatella., 

 Stomatia ,. 

 Haliotis . . , .. 



Tornatella . . 

 Pyramidella 



Third Family, 

 Les Melaniens!. 



Fourth Family. 

 Les P^ristomiens. 



Fifth Family. 

 Les N^ritac^s. 



Sixth Family. 

 Les Janthines. 



Seventh Family. 

 Les Macrostomes. 



Eighth Family. 

 Les Plicac^s. 



rFluviatile Trachcilipodes with 

 1 two tentaciilce and an oper- 

 I cnlum, and only breathing: 



.^ water. The shells have the 

 I margin of the aperture dis- 

 • united, the right side always 

 L sharp : with an epidermis. 

 J- Animal the same as the preced- 



J ing family ; shell conoid or 



S subdiscoid; the margins of 

 [_ the aperture united. 

 rOperculated Trach^lipodes, and 

 j breathing water only ; some 

 I inhabit fresh water, others 

 j are marine. Shells senai- 

 •' globular or a flattened oval, 



\ without a columella, and the 

 j left margin of the aperture 

 forming a cover half over the 

 I aperture of the shell, like tlie 

 [_ deck of aboat. 

 r Shell marine, its aperture not 

 ■ at all closed, floating on the 

 I surface of the water; breath- 



J ing water only. The animal 

 I has a bladder attached to its 

 I foot, by which, when it is 

 ' inflated, the shell is sus- 

 L pended. 



r Shell not floating, aperture vei-y 

 I much widened, margin dis- 



< united, no columella or oper- 

 I culum. The animal breath- 

 [_ ing water only. 



{Aperture of the shell not widen- 

 ed, and plaits on the colu- 

 mella : the animal breathing 

 water only. 



