324 Notes on the Mollusean Fauna of Northern Illinois. 



Genus Flanorbis- — (Guet). 



Pla. glahratus, Say. Pla. campanidatns, Say. Pla. trivolvls, Say. 

 JPla. cicarinatiis, Say. Pla. dejlechis, Say. Pla. parvus, Say. 



Segmentina — (Fl.) 

 S. armigera, Say. Very abundant. 



[Genus Ancyhis — (Geof). 



Anc. tardus, Say. Associated with this species may be fi)und the 

 nest of an insect, Phrygania. This nest resembles the valvata in 

 shape, and is built of sand and mud cemented together. 



Family Valvatidce. — Genus Valvata — (Muller). 



The two species, V. tricarinata, Say, and V. sincera, Say, are found 

 in abundance. These may eventually be united in one species. 



Family Viviparidce. — Genus Vivipara — (Lam). 



V. interiexia, Say. V. s^ihpurptirea, Say. V. contectoides, W. G. 

 B. The latter very numerous. 



Genus 3Mantho — (Bow). 



M. subsolidiis, Anth. This shell becomes thinner in the northern 

 part of the State and is called Integra. M. decisiis, Say. M. rufus, 

 Halde. M. coarctata, Lea. Forms resembling ohesiis and exilis also 

 occur. 



Genus Lioplax — (Teos.) 

 L. suhcarinata, Say. Abundant. 



Family Rissoidce. — Genus Amnicola — (G. & H.) • 



A. porata, Say. A. cincinnatiensis, Anth. Both these species are 

 abundant. 



Bythinella — (Tand). 



B. ohtnsa, Lea. Very abundant. 



Somatogyriis — (Gill) . 

 S. depressus. Try on. Abundant. 



Pomatiopsis — ( Teyon) . 

 P. lapidaria, Say. P. cincinnaiiensis, Lea. Very abundant. 



Family Strepomatidce — (Halde). 



