GASTEREOPODA PULHONEA. 



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 



be lower pair are not to he seen. 

 Those whieh possess no apparent shell, form in the Linnaean sys- 



I.-MI the p-im> 



I, i MAX, Lin. 



Which we divide a> follow> : 



t properly so called, Lam. 



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

 to the fore pan of the back, merely covering the pulmonary 



Mcluni:i . . . 

 .... Melanopsis. 

 Pirena . 



itn .. . 



Paludina. . . 

 Ampullaria. 



Vavleella 

 Neritina. . 

 Nerita .. 

 Natica . 



Janthiua 



Stomatia . 



i . 



Tonmtclla . . 

 lidella 



Third Family. 

 Les Mi'-luniens. 



Fourth Family. 

 Les P^ristoiniens. 



Fifth Family. 

 Les Ne'ritacte. 



Sixth Family. 

 Les Janthines. 



Seventh Faiuily. 

 Lea Macrostomes. 



Eighth Family. 



rFluviatile Trach&ipodes with 

 two tentaculx and nu oper- 

 culnm, and only breathintr 

 ^ water. The shells have t he- 

 margin of the aperture dis- 

 united, the right side always 

 L sharp : with an epidermis. 



r Animal the same as the preced- 

 ing family ; shell conoid or 

 \subdiscoid; the margins of 

 the aperture united. 

 TOperculated Trachflipodes, and 

 hreathing water only ; some 

 inhabit fresh water, others 

 j are marine. Shells semi- 

 *' globular or a flattened oval, 

 \ without a columella, and the 

 j left margin of the aperture 

 forming a cover half over the 

 aperture of the shell, like the 

 (_ deck of a boat. 



r Shell marine, its aperture not 

 at all closed, floating on the 

 surface of the water; breatb- 

 J ing water only. The animal 

 | has a bladder attached to its 

 I foot, by which, when it is 

 inflated, the shell is sus- 

 L pended. 



Shell not floating, aperture very 

 much widened, margin di-- 

 united, no columella or oper- 

 cuhnu. The animal breath- 

 ing water only. 

 f Aperture of the shell not \\hU-n- 

 I ed, and plaits on the colu- 

 \ incllii : the animal breathing 

 L water only. 



