26 ILLINOIS NATURAL HISTORY SURVEY MANUAL 



Among the early Illinois naturalists who made extensive 

 collections and added greatly to our knowledge of the MoUusca 

 of this state may be mentioned Robert Kennicott, who was 

 Director of the Chicago Academy of Sciences and who studied 

 the zoology of Illinois (1845-1885)*, W. W. Calkins of Chicago 

 (1870-1885), John Wolf of Canton (1865-1870) and H. A. 

 Differs of southern Illinois (1850-55). Later, another group of 

 men took up the study and greatly advanced our knowledge: 

 W. A. Nason of Algonquin (1865-1910), J. H. Ferriss of Joliet 

 (1890-1925), A. A. Hinkley of Rockford and Dubois (1895- 

 1920), W. A. Marsh of Aledo (1880-1900) and W. S. Strode of 

 Bernadotte (1890-1910). 



Two men who wrote little but who made good collections of 

 Illinois snails for others to study should also be mentioned: 

 George T. Marston of Green Bay, Wisconsin, and C. S. Hodgson 

 of Albion, Illinois. 



The collections of some of these students have been de- 

 posited in the Natural History Museum of the University of 

 Illinois, along with the loan collection from the Natural History 

 Survey, and the material is available for scientific study. Among 

 the collections are those of Nason, Ferriss, Strode, Hodgson and 

 the author. 



Physiography of Illinois 



The state of Illinois is well situated for the study of geograph- 

 ic distribution. It covers 5^ degrees of latitude, lying between 

 parallels 37 and 42 >^. A marked difference in climate exists 

 between the widely separated northern and southern boundaries. 

 In the southern tip near Cairo the weather is so warm that cotton 

 flourishes, and the climate is of a very temperate nature even in 

 the winter months; whereas in the northern part near the Wis- 

 consin border tamaracks grow, and the ground is frozen for a 

 large part of the winter. The difference in climate is reflected 

 in the fauna. 



Illinois is partly surrounded by water bodies. The great 

 Mississippi stretches along the entire western side of the state, 

 the almost equally large Ohio borders the southern, and the 

 Wabash flows along a portion of the eastern border. On the 



♦The dates indicate period of greatest activity. The author of this fieldbook, 

 who should also be mentioned among eminent conchologists of the state, began 

 his study of the land snails of Illinois in 1895. — Editor. 



