MOLLUSCS, VERMES AND HYDROZOA 
body partly translucent with 
the central portion light brown. 
The tentacles are short and 
mottled with black. It in- 
habits the Eastern coast States 
from Maine to South Carolina, 
and west to Ohio and the 
Northwestern States. The 
spawn is deposited in irregular patches of 50 to 100 and hatch in about 20 
days. This species is similar to Succinea, but may be distinguished by 
the spiral line on the shell and the fold on the columella. 
L. decidiosa, Fig. 166, has a somewhat inflated thin translucent light- 
ochre or brownish 34 inch long shell, showing faint lines of growth. The 

FIG. 165. Lymnaea columella, Enlarged. 
spire is rapidly attenuated to an acute 
point, and the five whorls are sep- 
arated by a deep suture, the aperture 
being one-half the length of the shell. 
The body is light yellowish-grey, 
minutely dotted with white; and the 
tentacles short, broad and translucent. 
Its range is from New England to the Mississippi and it inhabits rivulets 
and small lakes. 
L. catascopium, Fig. 167, is very similar to L. putris of Europe and 
has a smooth and polished 34 inch long greyish or yellowish-brown shell 
with lightly marked lines of growth, and is darker at the apex, with 

four or five convex whorls of 
which the body whorl is large,’ 
the suture well defined, the 
spire tapering to an acute point 
and the aperture one-half the 
length of theshell. The body 
is yellowish-brown sprinkled 

FIG. 167. Lymnea catascopium. with light-yellow spots; the 
tentacles are short and the translucent foot as long as the aperture. It 
inhabits the rivers and streams of Massachusetts and New York near 
Niagara Falls, and the Delaware and Schuylkill rivers; and is one of the 
most frequently met with species. It is often introduced into the aquarium 
with plants. The 20 to 40 eggs are deposited in a transparent yellowish 
capsule which hatch in about 16 days. 
All the native Lymnea should be only sparingly introduced into the 
aquarium as they make havoc with the plants. Some species sever the 
232 
