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 pair are not to be seen. 
Those which possess no apparent shell, form in the Linnaean sys- 
tem the genus 
Limax, Lin. 
AVhich we divide as follows ; 
'Li'sikx, 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 pulmonarv 
Genus Melania . . . 
.... Melanopsis. 
.... Pirena . . . 
1 
i 
Valvata 
Paludina 
Ampullai’ia. . . . 
Vavicella 
Neritina. 
Nerita . 
Natica . 
Janthina 
Sigai-etus , , 
Srftomatella , . . 
Stomatia ,. . 
Hiiliotis ..... 
Tornatella .... ^ 
Pyrainidella . . ( 
Third Family. 
Les M(^lanien.s. 
Fourth Family. 
Les Pdristomiens. 
Fifth Family. 
Les Ndritacds. 
Sixth Family. 
Les Janthines. 
SeA'enth Family. 
Les Maernstomes. 
Fhghth Family. 
Lea I’licaces. 
rFluviatile Trachelipodes Avith 
I tAvo tentaculae and an oper- 
I culum, and only hreatliing 
Avater. The shells have the 
I margin of the aperture di.s- 
I united, the right side ahvays 
(_ sharp : Avitli an epidermis. 
f Animal the same as the preced- 
J ing family ; shell conoid or 
A suhdiscoid; the margins of 
L the aperture united. 
j''Operculated Trachelipodes, and 
breathing Avater only ; some 
inhabit fresh Avater, others 
are marine. Shells semi- 
J globular or a flattened oval, 
h AA'ithout a columella, and the 
left margin of the aperture 
forming a cover half over the 
aperture of the shell, like the 
deck of aboat. 
p Shell marine, its aperture not 
' at all closed, floating on tlie 
J surface of thcAvater; breath- 
ing Avater only. I'he animal 
'j has a bladder attached to its 
I foot, by Avhich, Avhen it is 
' inflated, the shell is sus- 
L pended. 
r Shell not floating, aperture very 
I much Avidened, margin dis- 
< united, no columella or oper- 
I culum. The animal breath- 
ing Avater only. 
f Aperture of the shell not Aviden- 
J ed, and plaits on the colii- 
A mella : the animal breatldng 
L Avatcr only. 
