[lambk] fossil horses OF THE OLIGOCENE 47 



well preserved. The characters presented will not admit, in the opinion 

 of the writer, of its assignment to any already described species; all 

 point to its probable specific distinctness. 



This tooth is about the size of, or possibly smaller than, M. westoni, 

 but is more progressive in every way. There is an entire absence of 

 an internal cingulum, the cross crests are better developed and relatively 

 higher with steeper slopes. The protoconule is relatively larger, and 

 the metaconule, although defined, scarcely breaks the continuity of the 

 metaloph which unites in a decided manner with the ectoloph. The 

 protoconule is distinctly defined in the protoloph and connects closely 

 with the forward slope of the paracone. The hypocone has about the 

 same height as the protocone. The anterior cingulum is strong. Mr. 

 Gidley informs the writer that he " would expect to see the hypostyle 

 well developed were that portion of the tooth present." 



Mesohippus propinquus, sp. nov. 

 Plate II, figs. 3 and 1. 



2nd right upper premolar, worn {figure 4). 

 2nd left upper molar, unworn {figure 3). 

 2nd right upper molar, unworn. 



The above teeth characterize a species of Mesohippus that is regarded 

 as distinct from M. hairdi, Leidy, although closely allied to it and most 

 resembling it. 



They are of nearly the same size as those of M. hairdi, if anything 

 slightly larger, and on the whole more primitive. Their general pro- 

 portions are somewhat diiïerent. 



Measurements : 



p" a. p. -013 hij tr. -0135. 



m^ left, a. p. -012 hy tr. -0155, height of protocone -005, height 



of hypocone -0057, height of ectoloph -008. 

 m^ right, a. p. -0122 hy tr. -015. 



In the unworn tooth, figure 3 (left upper m^), the ectoloph is well 

 elevated above the cross crests in which the protocone and hypocone are 

 conspicuously higher than the conules. The hypocone exceeds the pro- 

 tocone in height. The protoconule is well defined and distinctly breaks 

 the continuity of the protoloph. The metaloph is fairly continuous 

 and shows a disposition to unite with the ectoloph which, however, it 

 does not reach. The hypostyle is connected at its inner end with the 



