160 



In a preliminary study, like the present one, it is desirable to record 

 rather fully the observations made in the region studied, because 

 we have so few descriptions of the conditions of life on our prairies. 

 An effort has been made to give for each species the date of obser- 

 ■vation or collection, the locality or "station" where found, observa- 

 tions on habits and life history, and the field numbers of the speci- 

 mens secured. These numbers illustrate how observations may be 

 accumulated, upon a large number of individuals, without the ob- 

 server's being familiar with them, or even knowing" their scientific 

 names. 



It is really surprising how little is recorded about some of the 

 commonest animals of the prairie and forest in zoological literature. 

 Other animals, particularly those of economic importance, are 

 treated rather fully, but generally with little relation to their natural 

 eiivironment. In this list it has been considered desirable not to 

 give an extended account of each kind of animal, but to refer to 

 some of the most important literature concerning it, so that one may 

 gain some general idea of the ecological potentialities of each kind of 

 animal. 



MOLLUSCA 



4 



Physid^ 

 Physa gyrina Say. 



Three half-grown young and an adult shell were taken among 

 swamp milkweed, Asclepias incaniata (Sta. I, ^), Aug. ii (No. 19). 

 All show distinct varices ; the last one formed on the adult shell is 

 very distinct. These scars mark a period of rest or slow growth 

 which was probably due to hibernation or the drying-up of the 

 swamp. Physa, as a rule, can not endure such extreme desiccation as 

 can Lyuuicca, and to that degree is indicative of a more permanent 

 water supply. Our specimens were all dead, but some of them so 

 recently that fly maggots came from them. 



Lymn^id^ 



Galha uinhiUcata (C. B. Adams). 



A single specimen of this small snail was taken among swamp 

 milkweeds (Sta. I, d) Aug. 11 (No. 18). Mr. F. C. Baker, who de- 

 termined the specimen, writes me that this is the first record of this 

 species for Illinois. Baker remarks ('ir, p. 240) that this species is 

 "abundant in still water in sheltered borders of rivers, in small 

 brooks, ditches, and streams, and in shallow overflows. Clings to 

 dead leaves or other submerged debris, or crawls over the muddy 



