Cope.) 386 {April 15, 
Measurements of Cranium. M. 
; § anteropos- 
Diameter crown third permanent premolar terior... .007 
transverse. .005 
Anteroposterior diameter crown first premolar......... 0045 
Diameters crown first true molar ee an ae 
anteropos- 
Diameters crown second inferior true molar terior 011 
transverse. .007%5 
Diameter of root of inferior canine near crown......... .0035 
Vertebra. The atlas is about as long relatively as that of the horse. Its 
transverse processes have more anteroposterior than transverse extent. 
The summit of the neural arch has a median ridge separating two grooves. 
The inferior surface of the centrum has a nearly median, obtuse hypa- 
pophysis. The axial facets are well separated below. The vertebrarterial 
canal pierces the base of the transverse process behind and below, and 
notches it deeply anteriorly. Above this notch the usual perforation of the 
arch is present. The axis is not relatively quite so long as that of the horse ; 
it is a little longer than in Hyrachyus cwimius, but rather shorter than in 
Hyracodon arcidens (Pl. CII, Fig. 7). The atlantal facets are spread well 
apart, and the articulating surface of the odontoid does not connect with 
them. The latter is rather long, is obtuse, and slightly recurved ; it has 
no raised borders. Between the atlantal faces the inferior surface is plane, 
Posterior to this the middle line bears a prominent keel. The diapophyses 
are long, narrow and recurved, and each is pierced at the base by the ver- 
tebrarterial canal. .The posterior articular face is but little concave, and a 
little oblique, and is a little wider than long. 
The succeeding cervicals regularly diminish in length, and become more 
strongly opisthocelous, the seventh having quite a ball in front. The 
sixth has a slender diapophysis directed posteriorly, and quite distinct from 
the wide and long parapophysis which is directed downwards and out- 
wards. The posterior angle of the latter extends as far back as the cen- 
trum. The seventh has only a flat transverse diapophysis. The first 
dorsal has a very stout diapophysis excavated below for the rib tubercle. 
The diapophyses of the third and fourth dorsals are not so stout. The ca- 
pitular fossee are large. The centra of the anterior dorsals are flattened 
below ; they are concealed in part by the matrix in this specimen. The 
neural spine of the sixth cervical is narrow, and is directed forwards. 
That of the seventh is vertical, and narrows rapidly from a base which is 
rather wide anteroposteriorly. The spines of the dorsals are wider, and 
are directed gently posteriorly ; they are probably long, judging from the 
size of their bases. ; 
Measurements of Vertedra. M. 
Length centrum of atlas on side........ salad ee wis eee 027 
ss “ i belO Wier se eee sas tasieear nnd -010 
Width oi se “« posteriorly ...........5- 030 
