161 



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

 ohrussa, 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- 

 [)ears to be a strictly shallow-water marginal form, and has consider- 

 able power of enduring desiccation. 



CRUSTACEA 



ASTACID^ 



Caniharus gracilis 'Bnwdy. 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, 191 1, and Aug. 9, 19 10 (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 SilpJiimn tercbiiitliiuaccitJii and Lepachys pin- 

 nata, and also at Station I, g. 



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

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

 19 1 2, burrows with fresh earth were numerous, far from any stream. 

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



Cainbanis diogcncs Girard. Diogenes Crawfish. 



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

 I, d (No. 8047A). The presence of this chimney 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. 



ARACHNIDA 

 Phalangiida 

 Phalangiidje 



Liohunuui polituin Weed. Polished Harvest-spider. (PI. XXX\'n, 



fig- 3-) 

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



under moist wood upon the prairie (Sta. I, ^) Aug. 8. Concerning 



