18 THE CHICAGO ACADEMY OF SCIENCES. 
land, Frankfort, Lemont, Homer, New Lenox, Lockport and 
Joliet. The territory consists principally of rolling prairies; 
swamps, except near the rivers, are absent. The drainage is 
into the Illinois, thence to the Mississippi River through the 
DuPage, Desplaines and tributaries of the Fox rivers. Wood- 
lands are found along the river banks which afford a retreat for 
the land snails. The fresh-water forms are abundant. The fol- 
lowing species are peculiar to this region: - 
Anodonta imbecilis. 
Quadrula parva. 
Quadrula plicata. 
Quadrula coccinea. 
Alasmodonta pressa. 
Unio hildrethianus. 
Lampsilis anodontoides. 
Lampsilis ligamentinus. 
Lampsilis spatulatus. 
Sphzerium transversum. 
Spherium truncatum. 
Spherium securum, 
Pisidium politum. 
Omphalina fuliginosa. 
Vallonia parvula. 
Pupa procera. 
Pupa holzingeri. 
Pleurocera elevatum intensum. 
Elimia livescens depygis. 
We find the following species to be equally distributed 
throughout our area: 
Anodonta grandis. 
Anodontoides subcylindraceus. 
Strophitus edéntulus. 
Alasmodonta complanata. 
Lampsilis luteolus. 
Unio gibbosus. 
Quadrula rubiginosa. 
Quadrula undulata. 
Sphzrium stamineum. 
Spherium striatinum. 
Sphzrium partumeium. 
Pisidium abditum. 
Vitrea arborea. 
Vitrea hammonis. 
Vitrea indentata. 
Conulus fulvus. 
Gastrodonta nitida. 
Gastrodonta minuscula. 
Limax campestris. 
Pyramidula alternata. 
Pyramidula striatella. 
Pyramidula lineata. 
Vallonia pulchella. 
Polygyra thyroides. 
Polygyra profunda. 
Polygyra hirsuta. 
Pupa contracta. 
Pupa curvidens. 
Succinea obliqua. 
Succinea avara. 
Succinea ovalis. 
Carychium exiguum. 
Carychium exile. 
Limnza desidiosa. 
Limnza humilis. 
Limneza caperata. 
Limnza cubensis. 
Limnza palustris. 
Limnza palustris michiganensis. 
Limnea reflexa. 
Planorbis trivolvis. 
Planorbis parvus. 
Segmentina armigera. 
Ancylus rivularis. 
Physa heterostropha. 
Aplexa hypnorum. 
Pleurocera elevatum. 
Elimia livescens. 
Amnicola limosa. 
Valvata tricarinata. 
Vivipara contectoides. 
Campeloma rnfum. 
Campeloma decisum. 
Campeloma subsolidum. 
