
MOLLUSCS, VERMES AND HYDROZOA 

S. obliqua, Fig. 161, has a % to 1% inch long, ovate, thin and fragile 
pale-green or amber shell, which is faintly striated and roseate in color at 
the apex. It has three whorls 
of which the body whorl is 
large and much _ expanded, 
and about % the length of the 
shell. Thespire is very small, 
the aperture oval and is two- 
thirds the length of the shell. 
The body has a yellowish- - 
brown color which shows through the semi-transparent shell. This snail 
is quite generally distributed in New York, Pennsylvania, New Jersey and 
Georgia. It is destructive to adie plants. 

FIG. 161. Succinea obliqua. 
S. retusa, Fig. 162, has a 44 to 7% inch long somewhat conical ovate- 
oblong very thin seller yellowish- ie minutely striated shell of three 
whorls, of which the body whorl 
constitutes nine-tenths of the 
entire shell and tapers gradually 
to the apex. The spire is short, 
the suture indistinct, and the 
aperture four-fifths the length 
of the. ‘shell. Phe body is a 
little longer than the shell, of a translucent greyish color marked with 
black spots. This snail is found quite generally in the Eastern and 
Middle States. 
Lymna&a. This numerously represented genus is found in stagnant 
and sluggish water, ponds and streams; feeding upon waste matter and 
aquatic plants, as all the genus are herbivorous and a few species also 

FIG. 162. Succinea retusa. Enlarged. 
carnivorous. ‘They are active, prolific and thrive in the aquarium, but are 
destructive and constant feeders, preferring the healthy growing plants to 
algae and decaying vegetation; though they are also effective scavengers 
and devour animal substances and food offal, and sometimes their own 
spawn. When bred in the aquarium they considerably loose their destructive 
habits and become feeders on alge. All are air breathers and will leave 
the water to rest upon aquatic plants, but only at long intervals. ‘The 
shells of this family are all dextral. 
L. stagnalis, Fig. 163, is the largest representative of this group, the 
shell reaching a length of 1% to 2inches. Itis usually of a greenish-white or 
yellowish-grey color; of six or eight whorls; of which the body whorl 1s 
larger, fuller and rounder than the others, which are drawn to a long, 
graceful dextral spiral, terminating in a finely pointed apex. The suture 1s 
230 
