528 



PROCEEDIXGS OF THE XATIOXAL MUSEUM. 



vol. 48. 



In the United States National Museum is a nearly complete skull 

 which belongs to a species of Equus, which was found in 1886 in the 

 region south of Hay Springs. Nebraska, and which has the number 

 7868. The exact locality is given on page 568. where is indicated 

 the place at which certain limb bones of horses had been discovered. 

 All these remains were collected by Mr. Hatcher and his party. 



Certain fragments of bone are missing from the skull, as seen from 

 above and from the sides; other parts are gone on each side of the 

 base of the skull and from the palate. The illustrations (pis. 32, 

 33), prepared from photographs, indicate the positions of the miss- 

 ing parts. Apparently nothing is missing that is necessary to an 

 understanding of the structure of the skull. The teeth are all present 

 in both the upper and the lower jaws; the incisor teeth are worn 

 down nearly to the bottom of the cups, but the premolars and molars 

 show less wear. The second molar has still a height of 65 mm. In- 

 asmuch as large canine teeth above and below are present, it is con- 

 cluded that the animal was a male. 



The following measurements have been secured from the skull. 

 In order to permit comparisons to be made there are presented like- 

 wise, in parallel columns, corresponding measurements obtained from 

 the skull of Equus niohrarensis, found in the same quarry and de- 

 scribed in 1913, 1 and from a skull of domestic horse (No. 843, Nat. 

 Museum). The dimensions within parentheses are taken from the 

 lower jaw of a slightly smaller and older horse (No. 174968 Nat. 

 Museum). 



Measurements of sic nils in millimeters. 



Distances. 



E. hatch- 



E. niobra- 



E. cabal- 



ert. 



rensts. 



Im. 



552 



530 



550 



300 



290 



300 



206 



200 



196 



615 



582 



602 



152 



137 



143 



364 



340 



362 



427 



420 



438 



114 



110 



129 



56 



47 



55 



230 



217 



213 



130 



123 



127 



76 



78 



75 



176 



158 



153 



236 



240 



220 



228 



218 



228 



210 



187 



188 



82 



70 



77 



48 



50 



53 



72 



75 



67 



40 



45 



45 



115 



105 



110 



68 



84 



70 



460 



467 



(472) 



90 



90 



(97) 



100 



96 



(82) 



102 



93 



(113) 



From middle of incisive border to front of foramen magnum 



From middle of incisive border to front of posterior nares 



From middle of incisive border to rear of notch between nasal and pre- 



m axilla 



FTom middle of incisive border to rear of occipital crest 



From middle of incisive border to front of pms 



From middle of incisive border to front of orbit 



From middle of incisive border to rear of orbit 



Width across mastoid processes 



Width across hinder nares 



Width across articulations for lower jaw 



Width from outside to outside of last molars 



Width from outside to outside of outer incisors 



Distance between fronts of orbits 



Distance between rears of orbits 



From middle of occipital crest to rear of orbit 



Width of skull on maxillary ridge at maxillo-malar suture 



Width of palate at last molars 



Width of palate at pm 2 



Distance across premaxillae at middle of nasal opening 



Least width of palate between i 3 and pm 2 



Distance between i 3 and pm 2 



Diameter of orbit, fore and aft 



From front of lower jaw to rear of ascending ramus 



Length of symphysis of lower jaw 



Height of jaw at front of mi 



Rear of i 3 to front of pni2 



iProc. U. S. Nat. Mus., vol. 44, p. 576, pi. 69, figs. 3-4 ; pi. 70; pi. 

 text figs. 19-23. 



71, figs. 1, 2; 



