1884.) 551 [Cope. 
The canines are much larger, with cylindrie root and flat, incisor-like 
crown. The first premolar is still larger, and is of about the same form as 
the canine, from which it is only separated by a slight divergence of the 
crowns. There are no diastemata, The second premolar has a compressed 
triangular crown, with a median ridge on the internal side. Its long 
diameter is diagonal, running outwards posteriorly. The long axis of the 
third premolar is similar, while the other teeth are more nearly in line. In 
the third premolar the fossa interior to the median internal heel is much 
deeper than that posterior to it. The corresponding fossa is still Jarger in 
the fourth premolar, while the crown has a heel in the form of a trans- 
verse curved crest, separated from the median heel on the inner side by 
a fissure. The true molars increase rapidly in size posteriorly, but not so 
abruptly as in the Pithecistes brevifacies. The internal crescents are very 
flat, and the posterior edges of theit columns project moderately. The ex- 
ternal crescents are very convex. The prismatic character of the teeth in- 
creases much posteriorly, so that the roots of the third tooth are short, and 
the crown long. The enamel is minutely rugose. 
The third superior temporary molar has two pairs of crescents. The an- 
terior pair are, however, not so well developed as the posterior pair and the 
two valleys are soon obliterated by wear. The crescents are equal in the 
fourth temporary molar. The fourth permanent premolar is protruded at 
least as soon as the third true molar, sooner than the posterior column of 
the latter. In this it differs from the Oreodon culbertsoni, where the last 
true molar is protruded first, and is a cotemporary of both the third and 
fourth deciduous molars ;* and the 0. gracilis, where the last true molar is 
a cotemporary of the third deciduous. 
In the inferior temporary dentition, the lobes of the last molar are sub- 
equal, the posterior one being a little the larger. The protrusion of the 
last true molar is also probably delayed until the shedding of the deciduous 
series, as in the superior series ; but my specimens are either very young 
or fully adult, and therefore I cannot demonstrate this point as fully as in 
the case of the superior series, 
Measurements of Skutt. 
M. 
Length from condyle to front of canine inclusive...... He's he 
Mh Mi TH OUG) UNG, (AMIRI ww eVien bes oc SOLO 
hd bg i *€ palatonareal notch,....... vies, SOON 
: : ‘* anterior line of glenoid cavity. .088 
Depth of occiput, including condyle...... Ne rye 041 
«« at middle of orbit, exclusive of teeth............ .087 
ne ‘« infraorbital foramen ST On W eaten a: Sata 016 
« “ premaxillary border Stata Uatitoctes sl Wiest eras .02: 
Width at Ms dh BWVOVGisass doa URS 
Phy SM OUW GIR OLUEGS sy cv Vices isl ere Gigs VEN Ok oe hs SUBS 
*Leidy. Ancient Fauna of Nebraska, 1853, p. 51, Pl. IV, figs. 1, 2. 
PROC. AMER, PHILOS. 800, xxi. 116. 8k. PRINTED JUNE 24, 1884, 
