CONCHOLOGY. Ill 



M. Sayii.* M. plicata.* 



M. elevata.* M. inflata.* 



M. armigera.* N. conica.* 



M. multilineata.* M. catenaria.* 



M. proxima.* M. simplex. * 



M. Hydeii * M. excurta.* 



M. salebrosa.* M. annulifera.* 



M. bitaeniata.* . M. pyrenella.* 



N. leina.* M. coma.* 



M. nassula.* M. alveare.* 



M. trochiformis.* M. cylindracea.* 



M. elevata.* M. vestita.* 



M. laqueata.* M. caniculata.* 



M. semicarinata.* M. Virginica.* 



M. subularis* {Lea). M. tuberculata* {Leu). 



M. acuta.* „ M. elongata.* „ 



2. Genus Pirena. PI. X. 

 Jinimal. Much elongated, mantle prolonged into a canal at 

 the left side, but without distinct tube ; foot short, oval, with an 

 anterior marginal furrow ; head terminated by a depressed pro- 

 boscidiform muzzle ; tentacula very distant, thickly annulated, 

 dilated in the inferior half of their length, and having the eyes at 

 the summit of this dilation ; mouth a terminal and vertical slit, 

 without labial tooth, and with a very small tongue ; a single long 

 and narrow branchia. 



Sliell. Distinguished from the preceding genus by having a 

 sinus at the base, and another at the summit ; turreted ; aperture 

 longitudinal, right Up sharp, base of the columella inclined to the 

 right. Inhabits the rivers of India and Africa. One species is 

 found in America. Six species. 



Pirena terebralis. Pirena aurita. 



P. cancellata. P. spinosa. 



P. granulosa. 



P. scalariformis.* 



3. Genus Melanopsis. PI. X. 

 Animal. As preceding genus. 



