308 University of California Publications in Geology [Vol. 12 



Measurements of Lower Cheek Teeth and Mandible of Equus bautistensis, 

 Eeferred Specimens — (Continued) 



' ■ ' ■ No 23196 No. 23913 



mandible mandible 



Mi, anteroposterior diameter 28.2 mm. 29.7 mm. 



M.2, transverse diameter 12.9 14.4 



M;, anteroposterior diameter of metaconid- 



metastylid column 14 14.7 



Mj, anteroposterior diameter 34.4 



M3, transverse diameter . 13.7 



M5, anteroposterior diameter of metaconid- 



metastylid column . 13.1 



Limb elements. — The unciform facet of the metacarpus (pi. 45, 

 fig. 1) is largely developed. Specimen no. 23460 is fully as large as 

 the metacarpus referred to Equus pacificus (Univ. Calif. Coll. Vert. 

 Pal. 2410), and is considerably shorter than that of a new form from 

 Idaho (Univ. Calif. Coll. Vert. Pal. 3836c). In comparison with the 

 fore cannon bone an unassociated hind cannon bone, specimen no. 

 23459 (pi. 45, fig. 3a), is unusually light and long (measuring 285 mm. 

 versus 242mm. in the former), it is more slender and slightly shorter 

 than that of E. pacificus. This more than proportionate lightness of 

 the posterior element is indicated by further fragmentary remains. 

 The cuboid facet of the metatarsus is large, but is not so square in 

 shape as in the modern draught horse. The cuboid facet of the 

 calcaneum is also less developed posteriorly than in the latter (pi. 45, 

 fig. 3c). 



Measurements op" Hind Limb Elements of Equus bautistensis 



Metacarpal III, no. 23460, greatest length 242 mm. 



Metacarpal III, no. 23460, transverse width of distal troch'ea 54 



Metatarsal III, no. 23459, greatest length 285 



Metatarsal III, no. 23459, transverse width of distal trochlea 53 



Phalanx I, no. 23459, greatest length 92 



Phalanx I, no. 23459, greatest length 95 



Phalanx II, no. 23459, greatest length 57 



Phalanx II, no. 23459, greatest length 59 



Comparisons. — Compared with the figured dentition of Eqxius scotti 

 Gidley that of Equus bautistensis may be of a slightly more primitive 

 type, in that : ( 1 ) the upper cheek teeth are narrower transversely, 

 the molars are slightly shorter anteroposteriorly, and their mesostyles 



