Peterson : Osteology ok OxvDAcrvLus. 473 



longer than that of an adult specimen of Camcliis hactrianiis and the 

 unguligrade structure of the phalanges are more specialized than those 

 of the recent camels. ■■' On the other hand the narrow and elongated 

 cranium, the unreduced dentition, the separated metapodials and many 

 minor characters present would be considered as primitive. 



Probable Habits of Oxydactylus. 

 From the osteological structure of Oxydactylus, it would appear that 

 specialization had been in the direction of those characters required 

 for greater speed and endurance. The trunk became relatively lighter 

 and the limbs stronger and more elongated than in earlier forms. The 

 usual habitat was probably an open plain where long journeys from 

 pasture grounds to water were necessary. 



Geological Notes. 



Owing to the somewhat uniform character of the entire sedimentary 

 mass of the Loup Fork series in Sioux County, Nebraska, some diffi- 

 culty was met with in intelligently labeling material gathered from the 

 different horizons. The Gering and Arickaree sandstones of Darton ^* 

 attain a thickness of 900 to 1200 feet in this locality. For con- 

 venience and precision the writer divided the beds, temporarily, into 

 three divisions. The Lower Loup Fork, the Dcemonelix ; and the 

 Upper Loup Fork. This arrangement was thought of importance in 

 connection with the work carried on. Mr. Hatcher" divided the 

 Arickaree sandstones into two distinct horizons overlaid by a third, 

 the "Nebraska Beds" of Scott. In an ascending order the Loup 

 Fork beds in this locality are according to Hatcher as follows : 



The Gering Sandstones, consisting of some 200 feet of laminated, 

 massive and cross-bedded sandstones. 



The Monroe Creek Beds, composed of some 300 feet of very light 

 colored, fine grained, not very hard, but firm and massive sandstones. 



The Harrison Beds, composed of about 200 feet fine-grained, rather 

 incoherent sandstones. 



The Nebraska Beds, consisting of a series of buff-colored sandstones 

 of varying degrees of hardness and unknown thickness. The Nebraska 



^*It seems to be generally accepted that the peculiar cushion foot of the Tylopoda 

 was developed from the unguligrade condition. 



26 U. S. Geogr. S. Nineteenth Annual Report, Part IV, p. 735, 1897-98. 

 '^' Proc. Am. Phil. Society, Vol. XI, I, No. 169, pp. 11 6-1 17 



