120 



TITANOTHEEES OP ANCIENT WYOMING, DAKOTA, AND NEBRASKA 



Fish, reptile, and mammal Jauna contemporary with the titanotheres — Continued 



« Based upon a part of a "right upper molar," which from Mr. Lambe's figure appears to be a left lower molar, probably of a hypertragulid comparable 



to Heieromeryx. 



NOTES ON THE HABITAT OF THE FAUNA OF THE CLAY AND 

 SANDSTONE AS A WHOLE 



Matthew was the first to distinguish between the 

 upland forms, found chiefly in the clays (flooded 

 plains), and the lowland and aquatic forms, found in 

 the sandstones (river channels). The following dis- 

 criminations have been made: 



1 . Typical grazing group oj open plains. — Hyracodon, 

 Oreodon, Mesohippus, Eotylopus, Poehrotherium. Note 

 the cropping front teeth, associated with delicately 

 cut and progressively long-crowned grinders, small, 

 compact feet, and, except in Oreodon, long, slender 

 limbs. Colodon may belong here. 



2. Browsing group of hush country and forest. — 

 Titanotheres, Metamynodon, Caenopus, lEntelodon, 

 1 Anthracotherium, lAncodon, ''.Agriochoerus. All large- 



sized fighting beasts, with coarse, heavy enamel on 

 cheek teeth; front teeth adapted to lip browsing. 

 Metamynodon may very likely have been amphibious ; 

 the others probably were not. Entelodon is somewhat 

 of an enigma; Sus is the nearest analogue but not a 

 close one. 



3. Small hush or forest-dwelling browsers. — Hetero- 

 meryx, Leptomeryx, Trigenicus. Analogous to the 

 modern tragulines and probably of similar habits. 



4. Carnivora. — The hyaenodonts are analogues of 

 the wolves. The ancestral canids are analogues of the 

 mustelines and viverrines. True mustelines are 

 scarce. Dinictis is the only cat. 



5. Rodentia. — Rabbits much like modern "cotton- 

 tails" of the Great Plains. Heteromyids have ap- 

 peared, but no true mice (Muridae) imtil the middle 



