MOLLUSCS, VERMES AND HYDROZOA 
a ———————————— 
Orper Putmonata.—Shell either spiral, conical, merely a calcarious plate, or altogether 
rudimentary; no operculum in freshwater species, 
breathing by a simple pulmonary sac; coming to 
the surface to breathe. 

Family Succineade—Shell imperforate, thin, ovate or oblong; aperture large, no 
operculum, breathing by lungs. 
Genus Succinea—S. obliqgua, S. retusa. 
Family Lymnzide—Shell thin, spiral or conical, no operculum, eyes sessile, breath- 
ing by lungs. 
Genus Lymnza—L. stagnalis, L. palustris, L. columella, L. decidiosa, L. 
catascopium. 
Genus Planorbis—P. dicarinatus, P. campanulatus, P: trivolvis. 
Genus Segmentina—S. armigerus, S. wheatleyi. 
Genus Ancylus—A. rivularis, A. parallelus. 
Family Physide 

Shell sinistral, oblong, thin, spire acute, aperture narrow oval, 
no operculum, breathing by lungs. 
Genus Physa—P. heterostropa. 
Genus Aplexa—d. hypuorum. 
Neritina. These snails are not generally distributed and are seldom 
met with. They have semi-globular shells consisting of an abrupt, flat 
spiral with crescent-shaped aperture and are rarely over a half inch in 
length. 
N. reclivata, Fig. 142, the larger native species, has a thick, strong 
globose-oval shell of greenish-olive color undiluted with faint green lines, 
polished on the under side, three-quarters inch long, consisting of three 
whorls, of which the 
body whorl takes 
up almost the entire 
shell and the spire 
very short and al- 
most always eroded 
by the action ot SENN 
peice thes water: FIG. 142. Neritina reclivata. Enlarged.* 
The aperture is about four-fifths the length of the shell. ‘The body 
is pale grey clouded with black, the head dusky, the tentacles long 

and rodlike, the eye prominent and placed on pedicels at the outer 
base of the tentacles, which are marked by darker or black lines. The 
wingshaped operculum has the fanlike striations spread from a nucleus at 
the upper margin. The snail is native to Florida. Its movements are 
slow and it does not survive in the aquarium. It is oviparous, laying from 
18 to 36 eggs on plants and stones which hatch in 14 to 16 days. 
N. showalteri, Fig. 143, is a very rare smaller snail native to Alabama. 
Its 14 to 34 inch long rather thick shell is smooth, round, semi-translucent, 
*The bar, in all cases, indicates the true size. 
221 
