910 



HISTORICAL GEOLOGY. 



Above the Titanotlierium beds lie the Oreodon beds, so named from a 

 characteristic Artiodactyl, between the Hog and Deer in structure. Pig. 

 1536 represents, natural size, the skull of the species, Oreodon gracilis of 

 Leidy. 



The Oreodon beds have afforded, besides species of several genera occurring 

 in the Titanotherium beds, remains of Tapir-like Ungulates of the genus 



1536. 



Oreodon gracilis. From Leidy. 



Protapirus ; also others related to the Rhinoceros, teeth from one of 

 which, of the genus Hyracodon (H. Nehrascensis of Leidy), are shown in 

 Fig. 1537. 



There were also species related to the Camel ; the earliest of true 

 Carnivores ; the earliest known of Bats ; of Squirrels of the modern genus 

 Sciurus, with many other Rodents ; and Marsupials of the modern genus 

 Didelphys, or that to which the Opossum belongs. 



Teeth of Hyracodon Nebrasceusis. Leidy. 



The following is a restoration, Jj the natural size, of Poehrotherium 

 labiatum of Cope, by W. B. Scott, a species of the Camel family, near the 

 Llama in its proportions. It is a fine example of a two-hoofed Artiodactyl. 

 Its characteristics will be understood after a comparison of the feet with 

 those of Phenacodus, Fig. 1517. The foot in Fig. 1538 includes the part 



