214 . Fresh- Water Shells. 



wheu this is removed, the surface is shining and pearly, of an 

 emerald-green color, lighter on the keels. It is one of our most 

 curious shells. 



Valvata Pupoidea. — (Gould.) 



^^ Shell small, elongated-ovate, opaque, chestnnt-colored, 

 __^ when divested of the rough, dirty pigment which usually 

 adheres closely to it ; whorls four or five, minutely w^rinkled, 

 the posterior one small and flattened so as to form an obtuse 

 apex ; the others cylindrical, and so partially in contact as to 

 expose about one half of the cylinder ; the last entirely disjoined 

 from the preceding one for at least the half of a revolution ; aper- 

 ture circular, lip simple and sharp ; on looking at the shell from 

 below, no umbilical opening is found ; operculum horny, apex 

 central, elements concentric. Length y'^ inch, breadth -^^ inch. 



Found at Fresh Pond and other ponds, on stones and submerged 

 sticks ; and has been for many years in our cabinets marked as a 

 Paludi'ha. 



Animal very active ; head proboscidiform, half as long as the 

 tentacles, bi-lobed in front, dark, terminated with light ; tentacles 

 rather stout, light drab-colored, with a line of silvery dots on the 

 upper side, over the large, black eyes ; foot, tongue-shaped, as long 

 as the first whorl, dilated into two acute angles in front, light 

 drab-color ; respiratory organ occasionally protruded to half the 

 length of a tentacle on the right side. 



This species is w^idely distinguished from all other described 

 ones by its minuteness, its elongated form, and its vrant of an 

 umbilicus; of which characters the last two seem to arise from the 

 loose manner in which the whorls arc united. 



Amni'cola Porata. — (Say.) 



i% ^^ Sliell minute, conic-globose, thin, translucent, 



^© fcmootij, or with most delicate lines of growth ; 



^ vaiying from a bronze-green to a light olive-green 



color, but usually invested v/ith mud; whorls four or less, very- 

 convex, and flattened near the suture, so as to present a conspicuous 

 shoulder ; the last whorl rather more than two thirds the length 

 of the shell, and as broad as Jong ; suture deeply impressed, almost 

 channelled ; aperture nearly circular, both lips being about equall}"- 

 curved, and uniting posteriorly at a broad angle ; lips sharp, in 

 some instances a little everted ; inner lip, at maturity, barely 



