Farr.] ±K)^ [May 15, 



end of M. iii and the cuboid is slightly shorter, so that it articulates 

 ■with the distal end of cuboid instead of being confined to mere lateral 

 contact. The antero-internal angle of cuboid is accordingly somewhat 

 modified in shape to correspond with the changed outline of metapodial 

 iii. This is a tendency in the direction of M. intermedms of the Pro- 

 loceras beds, and a foreshadowing of the condition in the modern horse 

 which has such a large facet on the cuboid for the widely expanded proxi- 

 mal end of metatarsal iii. Between this condition and that where there 

 is only lateral contact with the cuboid, we find all the intermediate 

 stages. Again, there is a great deal of variation in the relative propor- 

 tions of the lateral digits to each other, and in the relation they bear to the 

 median digit. Sometimes the lateral digits are not much reduced and 

 are subequal in size, while again we find tlie lateral digits very much 

 reduced, and Mt. iv, at least proximally, is usually larger than Mt. ii. 



In 31. bairdi usually there is no confluence of posterior transverse 

 crest Avith the outer wall of tooth, usually separated from it by a large 

 interval, but occasionallj^ we get an individual in which there is actual 

 confluence, and we get all stages intermediate between these two ex- 

 tremes. We get individuals where the interval between outer end of 

 transverse crest and outer wall is less, and, again, others in which there 

 is a small process jutting inwaitl from the point of union of outer lobes, 

 toward the transverse crest, these separated by a verj- small interval, 

 and then we get complete confluence. These highly specialized forms 

 were, of course, not ancestral, but were prematurely modernized and 

 left no descendants. However, these individuals most specialized occur 

 highest up in the beds, showing that these variations are attempts in the 

 way of evolution. 



Mesohippus Copei. 



This is a new species of horse from the White River, wliich has just 

 been described by Osborn and Wortman.* In their description of the 

 type no specific characters other tlian those of size are given, by wliich 

 it may be distinguished from the two other species from this liorizon. 

 Tliis species was founded upon a complete half of a pelvis, femur, tibia 

 and part of a hind foot, together with a median metatarsal and one lat- 

 eral metatarsal of another individual, a collateral type. "These re- 

 mains indicate an animal of much larger size than those of M. interme- 

 dius, and, so far as we know, is the largest horse of the White River 

 epoch, even larger than Mesohippus {Anchitherium) prtestans of the 

 John Day." The species is undoubtedly well founded, but the material 

 in the Am. Museum did not permit the establishment of good siiecific 

 characters. I have studied carefully the material upon which the species 

 is founded and have been able to refer some material in the Princeton 

 Collection to this species. Tliis material consists of the distal end of a 



* Bull Am. Mus., Vol. vii, pp. 352-35S. 



