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University of California Publications in Geology [Vol. 11 



A portion of a large, low, wide hoof, no. 21468, evidently repre- 

 sents Hypohippus. 



A number of large astragali (fig. 31) show the wide and relatively 

 shallow trochlea distinguishing this genus from Merychippus, in 

 which the groove is narrower, deeper, and relatively sharper. A very 

 large calcaneum evidently represents Hypohippus. 



29 



Fig. 29. Hypohippus, near affinis (Leidy). Phalanges 1 and 2, no. 21216, 

 X %. Barstow Miocene, Mohave Desert, California. 



Fig. 30. Hypohippus, near affinis (Leidy). Phalanx 1, no. 21211, X %. 

 Barstow Miocene, Mohave Desert, California. 



Fig. 31. Hypohippus, near affinis (Leidy). Astragalus, no. 21467, X %. 

 Barstow Miocene, Mohave Desert, California. 



Judging from the size of the limb elements Hypohippus furnished 

 the largest members of the Equidae of the Barstow fauna. 



Measurements 



Phalanx 1, digit III, no. 21216 



Greatest length 49.3 mm. 



Greatest proximal width 40.7 



Phalanx 2, digit III, no. 21466 



Greatest length 30 



Greatest proximal width 43 



Astragalus, no. 21467 



Greatest length 54.5 



Least width across trochlea 41 



Calcaneum, no. 21465 



Greatest length 106 



The proximal end of a very large metacarpal III (no. 21406, 

 locality 2056, fig. 32) differs from the type of the Merychippus-like 

 forms of the Barstow fauna and may represent Hypohippus. In 



