MOLLUSCS, VERMES AND HYDROZOA 



Order Pulmonata. — 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 Succineads — Shell imperforate, thin, ovate or oblong; aperture large, no 



operculum, breathing by lungs. 

 Genus Succinea — S. obliqua, S. retusa. 

 Family Lymnasidae — Shell thin, spiral or conical, no operculum, eyes sessile, breath- 

 ing by lungs. 

 Genus Lymnjea — L. stagnalis, L. palustris, L. columella, L. decidiosa, L. 



catascopium. 

 Genus Planorbis — P. bicarinatus, P. campanulatus, P: trivolvis. 

 Genus Segmentina — S. armigerus, S. wheatleyi. 

 Genus Ancylus — A. rivularis, A. parallelus. 

 Family Physidse — Shell sinistral, oblong, thin, spire acute, aperture narrow oval, 



no operculum, breathing by lungs. 

 Genus Physa — P. heterostropa. 

 Genus Aplexa— y/. hypnorum. 



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 



acids in the water. tig. i^^. mrui.a r.cli-va,a. 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 ^ to ^ inch long rather thick shell is smooth, round, semi-translucent, 



*The bar, in fell cases, indicates the true size. 



