161 



bottom of its habitat, in shallow water. Associated with Galba 

 obrussa, Aplexa hypnorum, and the small planorbes (Baker). In 

 ditches and brooks in pastures (True). Common in damp places 

 and in ditches along roads where water collects only in rainy weather 

 (Nylander)." 



Our specimen was taken where the water was very shallow (only 

 a few inches deep) and overgrown with vegetation. This species ap- 

 pears to be a strictly shallow-water marginal form, and has consider- 

 able power of enduring desiccation. 



CEUSTACEA 



ASTACmiE 



Cambarus gracilis Bundy. Burrowing Prairie Crawfish. ( PI. XXXVI. ) 

 The prairie crawfish was abundant at Sta. I, d, on the wet parts 

 of the prairie. T. L. Hankinson dug some specimens from their 

 holes, which proved to be of this species. Specimens were captured 

 Apr. 23, 1911, and Aug. 9, 1910 (No. 7442). 



Crawfish burrows were observed to traverse the dense yellow 

 clay with which the railway embankment had been built over a 

 swampy place at Sta. I, d. Burrows were also observed at Sta. I, e, 

 among the colony of Silphium terebinthinaceum and Lepachys pin- 

 nata, and also at Station I, g. 



I have found the characteristic claw pf this species on wet prairie 

 along the railway track at Mayview, 111. At this time, September 26, 

 19 12, burrows with fresh earth were numerous, far from any stream. 

 (No. 482, C. C. A.) 



Cambarus diogenes Girard. Diogenes Crawfish. 



Crawfish of this species were taken by T. L. Hankinson at Sta. 

 I, d (No. 8047A). The presence of this chirrtney builder at this sta- 

 tion suggests that the numerous chimneys shown in Figure 2, Plate 

 IIIB are in part the work of this species though they are in part also 

 the work of gracilis. 



AKACHNIDA 



PHAtANGIIDA 

 PHALANGraJiE 



Liobunum politum Weed. Polished Harvest-spider. (PI. XXXVII, 

 fig. 3.) 

 Two small phalangiids, both probably of this species, were found 

 under moist wood upon the prairie (Sta. 1, g) Aug. 8. Concerning 



