Mammalian Fossils front Devil's Giilch 13 



(407 mm.) transversely, by 14 inches (356 mm.) vertically. The 

 thyroid foramen is 7>^ X 4/^ inches (192 X 115 mm.). The 

 extreme width across the iha is 56 inches (1424 mm.). 



Hypohippus Matthewi sp. nov. 



Two maxillae of a very large Hypohippus, together with scat- 

 tered lower teeth, and numerous skeletal parts, were found below 

 but near Quarry No. i, Devil's Gulch. Some of these bones occurred 

 in a bed of white diatomite, about 10 inches thick, and about 150 

 feet long. Several complete feet, and numerous limb bones were 

 dug out of this diatomite, and were so faultlessly preserved that 

 it may be said, a better matrix cannot be found. The feet found 

 in the diatomite confirm the belief that this genus is tridactyl. 

 Hypohippus is a horse of forest adaptation. Several species are 

 known, notably Hypohippus affinus, H. osborni, and H. equinus. 

 Hypohippus matthezvi exceeds all of these in size. It is undoubt- 

 edly the largest member of the genus known as yet. 



Hypohippus matthezvi, named for Dr. W. D. Matthew, though 

 closely resembling Hypohippus affinis is much more hypsodont, 

 and is from one-fifth to one-eighth larger, as may be seen in the 

 accompanying half tone figures, which are exact size. It is pre- 

 sumably a later mutant. 



Hypohippus is closely related to Anchitherium, and is classed as 

 the most advanced member of the Anchitheres. The briefest de- 

 scription of the teeth of Hypohippus matthezvi is that they are 

 Mesohippus enormously enlarged. They are strikingly similar 

 point for point. It should be noted that Anchitherium, the Euro- 

 pean form, is closely related to Mesohippus, the American. 



Though represented at one time by roving herds of many varie- 

 ties, horses are now reduced to but one family, the Equidae, which 

 includes the three living genera, Assinus (the wild asses), Hip- 

 potigris (the zebras), and Equus (the true horses). 



Our modern horses, though monodactyl in one sense, are tri- 

 dactyl in another, for the two splint bones are ancestral toes per- 

 sisting at the present time. 



Ancestral horses are characterized by long bodies, arched backs, 

 short limbs, short necks, short teeth, long tails, and polydactyl 



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