
MOLLUSCS, VERMES AND HYDROZOA 

occurs from Maine to Pennsylvania and Ohio, and is very numerous on 
the muddy shores of the Delaware and Schuylkill rivers, 
A. granum is a very small species, not much larger than a pin’s head, 
found in ponds near Philadelphia. It has a slender, conic-ovate yellowish- 
brown shell, having four or five convex whorls, deeply impressed suture 
and orbicular aperture. It ranges from Lake Superior to Virginia. 
Gould mentions another species, 4. pallida, which has not been described 
as occurring in the Middle States. 
Biruynta. These small whorled snails are usually found in ponds, 
ditches, canals and slow streams of not too cold water. They are oviparous 
and water-breathing, differing principally from some of the smaller Physa 
in having the whorl of the shell dextral. They thrive fairly well in the 
aquarium but are vegetable feeding and indifferent scavengers. 
B. tentaculata, Fig. 157, has a glossy grey or horn-colored conical 3 to 
¥% inch long shell of six rounded whorls, with a distinct suture and pointed 
apex. The body whorl 
takes up more than _ half 
the length of the shell. 
The body is almost black, 
spotted with yellow and the 
divergent filiform tentacles 

. are long and slender. The 
FIG. 157. Bithynia tentaculata. Enlarged. eyes are black and set at the 
base of the tentacles and the obovate operculum calcarious and brittle. It 
is a harmless oviparous snail, feeding principally on decaying vegetation. 
Found quite generally in the Eastern and Middle States. 
Meraniup. It should be noted of this family that it contains many 
genera and hundreds of species. Almost every river drainage system of 
the world has either distinct or closely allied forms; those of the United 
States being the Strepomatide, of which there are many local genera, the 
most common of the Eastern and Middle States being the Goniobases and 
Anculosa of the Hudson, Susquehanna, Delaware and Potomac basins. 
For brevity these only are described, the others are closely related similar 
forms. 
Gontosasis. This genus has most beautiful conical or fusiform 
shells, showing faint lines of growth and often series of longitudinal ridges 
on the seven to ten whorls. Occurs quite generally in flowing waters. 
G. virginica, Fig. 158, is a very common species of the middle Atlantic 
coast States. Ithasa truncated turreted yellowish-brown 7% to 1 inch long 
shell, usually eroded at the spire. The eight to ten whorls are marked 
with a dull reddish line near the base of the whorls, with a second line 
228 
