WATER SNAILS. 
209 
tuted the genus Velletia for the reception of 
the present species. The shell is an elongated, 
subdepressed, and laterally compressed cone, of 
a light horn colour, and coarsely wrinked. 
A . oblongus differs from the river limpet in its 
habitats; it lives attached to the under side of 
leaves and stems of aquatic plants, as the yellow 
water-lily (Nuphar lutea), Alisma, Fotamogetons, 
and Sparganiums , and on the dead leaves of 
trees that have lain some time in the water; 
in still and gently flowing waters, as canals, 
lakes, and ponds. 
The present species is more active than its 
ally; it glides quickly, with a perfect appear¬ 
ance of immobility in its plan of locomotion; but 
it may be observed turning its head from right 
to left, under the shell, during its march. The 
tentacles alone are capable of being extended 
beyond the shell; they are cylindrical, obtuse, 
slightly contractile, and, from their extreme 
tenuity, appear white; but, seen through a lens 
by the aid of sun-light, they are slightly tinged 
with black. The eyes can be seen by viewing 
the animal from the side; they are sessile, very 
large, and black, somewhat angular or rounded. 
They never leave the water, and occupy them¬ 
selves with cleaning off the green matter which 
is attached to submerged plants and bodies. 
p 
