314 [Dec. 7, 
Cope.] 
Academy of Philadelphia, 1883, p. 80, and two species were mentioned, 
O. pelwidens (type) and ©. angulatus. The former of these is from the 
Puerco, the latter from the Wasatch formation ; the former is the larger 
species ; the latter quite small. I now add two species to the genus which 
are intermediate in dimensions between those already known. 
I. Posterior cingulum of superior molars with large tubercle. 
Large species ; O. pelwidens ; small species, C. truncatus. 
II. Posterior cingulum with small tubercle ; small species ; C. angulatus. 
III. Posterior ciugulum without tubercle; small species; @. sémplem. 
In the @. truncatus the posterior singular (inner) tubercle reaches the 
largest development, but is not present on the cingulum of the last supe- 
rior molar. The anterior cingulum is weak on that tooth and on the first 
true molar, but on the second it is thickened into a small anterior or 
inner tubercle. This, with the posterior inner, gives the crown a truncate 
internal outline, as is also the case in the O. peloidens. The intermediate 
tubercles are distinct, and the external cusps are separate at the base. An 
external cingulum. The fourth premolar has a triangular base ; a single 
compressed external cusp, and a small acutely conical internal one. The 
internal tubercle is small and acute on the third premolar. The second pre- 
molar is small and probably one-rooted, and it is possible that there is no 
first premolar. The canine is directed vertically downwards, and the base 
of the crown is oval. 
3esides the considerably smaller size, the posterior internal cusps are 
relatively larger than in O. peloidens. 
Measurements. M. 
3 Length of superior dental series including canine...... .039 
Length: Of tous MOlat COTO viv wae eu iviess erase varnis Acide evra is Oka 
Migitotere ont ti f anteroposterior..... Pace ee mcm (0: 
\ transverse. .... oh edule een rues varerinOUe 
Tibictere: Doane av { AVUCTOPORLOHIOL We nw ides dion vee wk 004. 
S CYOMSVCVSC Wa We ee si se aioe va cele COUT 
¢ ay ror lay 
iametora Mu { SECOTOMOSUSTION tie evsldicro vig ane: ateeivielwia }OUD 
CTH TOVOTRA Ley ch Vea aciieer abe ewe nk Wl0Od 
{ ANCELOPOSLETION s hewseio esd owevens views HOU00 
Diameters m._ iii- 
ltransverse..... ee pe ae Racike wxttiay ; W000 
Two individuals from New Mexico. D. Baldwin. 
CHRIACUS SIMPLEX, Sp. nov, 
This species is represented by a part of the left maxillary bone, which 
supports the true molars except a part of the last one ; and by parts of the 
mandible, with the first and second true molars, and perhaps one of the 
premolars. The true molars are about the size of those of the O. truncatus, 
but of very different detailed structure, as already pointed out. The pos- 
terior cingulum is stronger than the anterior, but does not support a trace 
of a cusp, and they do not unite on the inner face of the crown, External 
ae 
