568 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. 48. 



is relatively higher in front than in any of the other specimens, 

 although as a whole it is a less heavy jaw. This large jaw presents a 

 ratio quite different from that of Soergel's specimen, while the jaw 

 of the Arabian presents the same ratio as Soergel's. It needs to be 

 noted that the numbers in the last two columns of the table given 

 above are quite different from those in the third column ; and, besides, 

 are somewhat different from each other. The conclusion which one 

 must reach is that there is among the domestic horses and probably 

 all others more or less variability in the lower jaw, as there is in all 

 other structures. Even in any unmixed species the lower jaw must 

 be subject to great variations due to the state of development of the 

 teeth. The author regrets that he has not the time to test on the 

 zebras in the National Museum Soergel's indices and many others 

 which have been proposed. 



5. ON THE LIMB BONES OF CERTAIN FOSSIL HORSES. 



In the year 1886 John Bell Hatcher made a collection of verte- 

 brate fossils in the region south of the present town of Hay Springs, 

 Nebraska, for Prof. O. C. Marsh, then connected with the United 

 States Geological Survey. From Mr. J. W. Gidley the writer learns 

 that the exact locality is on the south side of the Niobrara Eiver, 

 about 15 miles south of Hay Springs ; and it is evidently in township 

 29 north and 47 west. The fossils occurred in a very restricted area 

 and in a deposit of loose sand. These fossils are now in the Na- 

 tional Museum. Dr. W. D. Matthew has given a list of the species 

 of vertebrates found in that neighborhood, probably in the same 

 quarry. Besides extinct horses, the list includes Mylodon, Cos- 

 toroides, Capromeryx, and three species of camels. 1 



In the collection at the National Museum there have been found 

 packed together in the same box a right fore and a right hind leg 

 complete with corresponding parts of the shoulder and pelvic girdles. 

 They are regarded as having all belonged to the same individual. 

 The fore leg has the number 7863 ; the hind leg the number of 7924. 

 These were not accompanied in the package by any skulls or teeth, 

 and it is therefore not possible to determine exactly to which one 

 of the several species of horses which lived in that region they be- 

 longed. They are here referred provisionally to Equas laurentius, 

 the smallest known horse of that region. It is proposed to describe 

 these bones and to make comparisons of them with corresponding 

 bones of an Arabian horse in the National Museum and with some 

 bones of other horses found in the same locality in Nebraska. 



In the first, third, fifth, and seventh columns are given the abso- 

 lute measurements, while in the second, fourth, sixth, and eighth 

 columns are presented the percentages which are obtained by com- 



iBull. Amer. Mus. Nat. Hist., vol. 16, p. 317. 



