THE NATURAL HISTORY SURVEY. 23 
V. GEOLOGICAL DISTRIBUTION. 
The geological distribution of the land and fresh-water 
species in the area is but imperfectly known. The shells of 
Unio, Elimia, Limnza, Planorbis and Ancylus have been found 
in considerable abundance in the beach at Evanston, near the 
University. In the township of Worth, three miles west of 
Morgan Park, the shells of Limnza, Planorbis and Physa have 
been found buried to the depth of several feet, and the speci- 
mens were perfectly preserved. The following species have 
been found and are in the collection of the Academy: 
Quadrula trigona—Corner Wrightwood Avenue and North Clark Street: 
excavations for building. 
Quadrula undulata—Corner Frederick and North Clark Streets: excava- 
tions for building. 
Quadrula sp. (apparently between trigona and rubiginosa)—Hall Street; 
excavations for building. 
Polygyra thyroides—Foot of Argyle Street, near the Lake. 
Limnza caperata—Worth. 
Limnza cubensis—-Worth. 
Limnza palustris—-Worth. 
Limnza reflexa—-Worth, and foot of Argyle Street. 
Limnza stagnalis—Near Calumet Lake. 
Physa heterostropha—Worth. 
Pleurocera elevatum—In beach, corner Sheffield and Lincoln Avenues. 
Elimia livescens—In beach, corner Sheffield and Lincoln Avenues. 
Elimia livescens—In beach, Balmoral Avenue north of Bowmanville. 
Campeloma decisium—Near Calumet Lake. 
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At Willow Springs, in the river bank, the following species 
were collected by Mr. Jensen: 
Anodonta grandis. Planorbis trivolvis. 
Unio gibbosus. Physa heterostropha. 
Quadrula rubiginosa. Cincinnatia obtusa. 
Sphzrium stamineum. Cincinnatia cincinnatiensis. 
Spherium simile. Amnicola limosa. 
In the sand banks east of Sheridan Drive and north of Grace- 
land Avenue, Mr. Jensen collected the following species: 
Spherium striatinum. Planorbis bicarinatus. 
Pisidium virginicum. Elimia livescens. 
Limnza desidiosa. Somatogyrus subglobosus. 
Limnza cubensis. Campeloma subsolidum, 
The same collector found the following species in a sub- 
fossil condition (buried in loam) at Bowmanville: 
Polygyra albolabris. Pyramidula alternata. 
Polygyra profunda. 
