Farr.l 1^^ [May 15, 



botli above and below the nieso-cuneiform and conditions the shape of 

 the head of M. ii, about one-half of the proximal surface being sup- 

 ported by the meso-cuneiform. Posterior to this facet the proximal sur- 

 face slopes abruptly downward and presents the above-mentioned facet. 

 About two-fifths of the internal surface of ecto-cuneiform is taken up 

 with a facet for metatarsal ii, which in M. hairdi extends upward pro- 

 portionately less on the ecto-cuneiform. The shaft is of about the same 

 dimensions proportionately as in M. bairdi and was closely applied to 

 M. iii proximally, but both the lateral metapodials curve outward dis- 

 tally. The distal end is merely an enlarged copy of that of the smaller 

 species, is high and compressed and the median keel is strongly devel- 

 oped. Metatarsal iii bears about the same relation to the lateral meta- 

 tarsals in size as in M. bairdi. In the latter we have a distinct facet on 

 M. iii, either lateral or proximal for the cuboid, but in the new species 

 M. iii does not touch the cuboid and the only facet on exterior surface 

 of the proximal end is that for M. iv. It is borne entirely by the ecto- 

 cuneiform and is quite large in proportion to the size of the lateral digits 

 and supports nearly all the weight and receives most of the impacts and 

 strains of the foot. The distal end is somewliat wider than the proximal 

 end. M. iii is quite a little longer than the lateral metatarsals, more 

 so than in M. bairdi. All the phalanges are slightly more massive pro- 

 portionately than in the smaller species. 



The pelvis in the Am. Mus. Collection referred to M. copei, I do not 

 regard as Mesohippus at all because it is too much specialized in its own 

 way to belong to a White River equine. It diflers very much from tliat 

 of M. bairdi and in some respects is more specialized tlian that of the 

 modern horse. If the reference to M. copei is correct, we have in this 

 species a very aberrant side line of the horse series. The pelvis under 

 discussion differs from that of M. bairdi in the following respects : 

 (1) The ilium expands very abruptly, almost directly in front of the acet- 

 abulum, while in M. bairdi it expands very gradually and begins its ex- 

 pansion a long way in front of the acetabulum (see PI. XIII and Fig. 4). 



(3) The angle of the ilium in M. bairdi and of all the known equines is 

 sharp, but in this specimen it is very much rounded. (3) The crest is 

 broad and stout instead of being narrow and elongate as in M. bairdi. 



(4) The border between angle and crest is very much less concave than 

 in M. bairdi and the horse. (5) The border of bone above acetabulum 

 is drawn out into a sharp crest even more pronounced than in tlie recent 

 horse. (6) The acetabulum is round as in Hyracodon, not elongate as 

 in M. bairdi and the horse. (7) The obturator foramen is broader in 

 proportion to its length than in M. bairdi. (8) The ischia turn upward 

 at an angle posteriorly almost as much as in the horse, wliile in M. bairdi 

 the ischium is in a straiglit line with the long axis of the ilium and does 

 not turn up posteriorly. In view of these great differences I cannot 

 regard the reference to M. copei as correct. 



In the American Museum there are a series of lumbar vertebraj which 



