FAUNA OF THE EQUUS BEDS. 83 



ures; that is, the transverse diameters are relatively greater. A meta- 

 carpus and metatarsus of a second (and probably the same) individual, 

 from Oregon present the same characters. Both are rather larger in all 

 their dimensions than the corresponding bones from Rock creek. Such 

 variations, however, are not greater than those that occur in the Equus 

 caballus. The phalanges are always relatively and absolutely smaller in 

 the E. excelsus than in the average E. caballus, as shown by a considera- 

 ble number of specimens. 



The peculiarities of the basioccipital and exoccipital bones are constant 

 in my material (four individuals from Oregon), and the relatively shorter 

 diastema in front, and less pioduction posteriorly, of the maxillary bone, 

 are always observable. My only specimen with a full series of teeth 

 (Plate XXII, Figure 4), shows that the M. iii is considerably smaller than 

 in the true horse. 



EQUUS MAJOR, Dckay. 



This horse is represented in the Staked Plains collection by parts of 

 four superior molars found together (No. 11). They display the typical 

 characters of the species. I have already identified this species from 

 Wharton county, in Southern Texas,* and Leidj' has reported fit from 

 various localities in the same State. 



The relations of the species of Equus found in the Cenozoic beds of the 

 Staked Plains, as to horizon, size, and complexity of enamel folds, may 

 be represented as follows: 



Equus bed. E. excelsus. E. semiplicatus. E. tau. E. major. 



Blanco. E. simplicidens. E. cumminsii. E. minutus. 



Goodnight' s. E. 9 simplicidens. E. eurystylus. 



The lines of the above diagram indicate relationship, but we do not yet 

 know enough of the species to determine th» phylogenies. 



HOLOMElSriSCUS, Cope. 

 Proceeds. American Philosophical Society, 1884, p. 16. 



HOLOMENISCUS HESTERNUS, Lcidy. 



Plate XXI, Figures 3, 4. 



Cope, loc. cit., p. 17; Auchenia hesterna, Leidy. Report U. S. Geol. 

 Survey Terrs., I., 1873, p. 255, Plate XXXVII, Figures 1, 3. 



A fine mandibular i-amus containing all the molars, with the symphysis 

 containing all the incisors but one, was obtained by Mr. B. S. Brown from 



♦Proceeds. Amer. Philos. Soc, 1892, p. 123. 

 tReport U.S. Geol. Survey Terrs,, 1873. 



