The Loess of North America. 



-Diaptomus sanguineus, J», geniculate ai 

 <?, right leg of 

 - " « tf.left « 



stagnalis, J 4 , fifth pair of 1 

 « ^geniculate an 

 « J, left antenna, 



" stagnalis, $, leg of fifth p 



.ischura lacustris, $ , fifth pair of le 



? , side view of £ 



aptomus leptopus, <j? , leg of fifth t 



« fright leg of i 



- 



25. — Epischura lacustris, J>, fifth pair of legs, 70. 

 26. — " " second maxilliped, X 8S- 



27— " « leg of first pair, X 70. 



29.— " " tf, fifth pair of legs, X 7°- 



fTtf /fc continued.) 



THE LOESS OF NORTH AMERICA. 



BY R. ELLSWORTH CALL. 



- 



Physical Geography of the Loess Era.— The Champlain epoch, 

 to which the loess belongs, was characterized by general conti- 

 nental depression, which lessened the area of the land and in- 

 creased the average temperature. Such a depress 



i followed 

 1 encroachment of the sea and its arms upon the land, 

 the effects of which would be greatest in the great central basin 

 of the continent. Hence there was a backing up of all the 

 streams and a general sluggishness or complete loss of their cur- 

 rents in the lower portions of their valleys. At their sources ex- 

 tensive denudation was in progress, and the material thus derived 



