1883,] 31 5 [Cope. 
cingulum present. External cusps rather smail, separate. Intermediate 
cusps present ; V large and distinct. Enamel smooth. 
The inferior trae molars support Vs; in the second the anterior is 
smaller and is more elevated than the posterior. The latter is continued 
as a raised posterior, and partly interior border of the heel, without promi- 
nent cusp. The crown has a distinct external and a very faint internal 
cingulum. In the supposed first true molar, the anterior V is more pro- 
longed anteroposteriorly as in the corresponding tooth of Mioclanus ferox, 
ete., and the fourth premolar of Phenacodus primevus. The anterior 
cusp is the lowest. The heel supports three low cusps, of which the ex- 
ternal has a crescentic section, and the posterior is the smallest. 
It is probable but not certain that the fourth premolar has an internal 
cusp, as the tooth, presumably this one, is injured at that point, Should 
the internal cusp be absent, this species cannot be referred to Chriacus. 
Measurements. M. 
Length of superior true molars... .eeereeseeses sees ance 0135 
Di fanteroposterior......... .005 
Jiameters of first true molars ) pe eat OR het Siete 
i anteroposterior. ..... .Q05€ 
Diameters of second true molars { ; I nm 
TPODRVELSC) se cua ys ous SOUS 
; , f anteroposterior......... .0084 
Diameters of third true molar 4 — t 
UETHYISVOLSGr sv cesis cue ccs CCUG 
f anteroposterior... .005 
Utransverse...... .0085 
: : f anteroposterior 0056 
Diameters of second inferior true molar 1 ; I , 
transverse,.... .0043 
Diameters of first inferior true molar - 
D. Baldwin, discoverer. 
TRICENTES CRASSICOLLIDENS, gen. et sp. NOV. 
9 
Char. gen. This genus is Ohriacus with only three premolars in the su- 
perior, and probably inferior series. The canines are well developed, and 
lateral in position, leaving space for small incisors, thus differing from the 
genera of the Mixodectidw, Miwodectes, Microsyops, and Cynodontomys, on the 
one hand, and from Necrolemur on the other. It has, so far as known, the 
dental formula of several genera of typical Lemuride, but differs from these 
in the following points. The orbit is open posteriorly ; the inferior molars 
have the anterior triangle of three cusps ; and the fourth inferior premolar 
has an interior cusp. I have demonstrated the last mentioned characters 
on the type, 7 erassicollidens only, but suspect its presence on some or all 
of the other species. In their details the superior true molars are like those 
of Mioclenus, as distinguished from those ot Pelycodus. 
To this genus belongs the Mioclenus subtrigonus, and probably, from the 
small size of its fourth premolar, the I, bucculentus. Tadd to these three 
a fourth, 7" inequidens, and remark that it is yet uncertain how many pre- 
molars are present in the Thriacus simplex. Should the latter possess 
three only, it will be properly referred to Tricentes. 
