XXVI I'lIKFACE. 



previously represented in this fauna in the United States, viz, the Mcsodonta 

 and Amhlypoda, the latter in several types of remarkable interest. 



In 1873 I fitted out an expedition at Greeley, Colo., and traversed the 

 Plains eastward toward Julesburg as far as the eastern branches of the Cedar 

 or Horse Tail Creek. Our route was parallel to the line of the so-called 

 Chalk Bluffs, which extend from west to east, forming a break in the southern 

 slope of the surface of the country from the dividing of the waters of the 

 North and South Platte. It consists of the Loup Fork sandstones resting on 

 a basis of the upper beds of the White River formation. The countr}- be- 

 tween the foot of the bluffs and the South Platte River is composed in its 

 northern part (if the White River tornialinii, Avl.icli jiresents exposures at 

 various points, and neai-er the river consists of the Laramie formation. On 

 this part of the expedition 1 obtained seventy-five species fnnn the White 

 River beds, and twenty-one from the Loup Fork. 



We then turned to the southwest, crossing the South Platte, and moved 

 up the valley of Bijou Creek towards the highlands of Colorado east of the 

 mountains, known as the Colorado divide. On this part of the expedition, 

 which was in charge of William G. Shedd, a number of interesting reptiles 

 of the Laramie period were discovered. The party then entered the South 

 Park and obtained a fine collection of the fishes of the Florissant shales 

 During this time I had made an excursion to Fort Bridger, Wyo., and had 

 supplemented the collections of the previous year. 



In 187 ^ I sent my assistant, J. C. Isaac, to Montana for the purpose of 

 examining the valley of Deep River for the fossiliferous deposits previously 

 reported to exist there by Captain Ludlow, United States Engineers, and 

 examined by Messrs. Dana and Grinnell of his party. The results were 

 satisfactory, a considerable number of fine specimens having been secured. 

 Mr. Isaac then passed southeastward into W3'oming, and explored the White 

 River beds of the southern parts of that Territory and the adjacent bor- 

 ders of Wyoming. 



The same year I employed Charles II. Sternberg to conduct an explora- 

 tion of the Cretaceous and Tertiary formations of Kansas. After a success- 

 ful search I sent Mr. Sternberg to Oregon, and Russell S. Hill took charge 

 of the expedition. Under his management an excellent collection of the 



