ARTIODAGTYLA. . 
325 
Width of the same.....-. 0. 022 
Length of the third true molar... 0. 029 
Width of the same... .. 0.022 
Width of the palate at the third premolar .. 0.034 
It may be noted from the above measurements that the first true molar 
is a good deal smaller than the second. 
PEOCAMELUS, Leidy. 
Proc. Phila. Acad., 1858, p. 89; Extinct Mammalia Dakota and Nebraska, 1869, p. 147. 
The dental formula of this genus is I. g ; C. j; Pm. |; M. |. The 
number of teeth of the superior series anterior to the true molars was left 
uncertain by Dr. Leidy, and I was able to complete our knowledge of it 
after an examination of Colorado specimens. I ascribed three superior 
incisors to this genus at that time, as they are possessed by the species 
which I named Procamelus heterodontus. Having obtained in New Mexico 
the nearly entire cranium of the P. occidentalism I find that the single lateral 
incisor found in the existing Camelidce is the only one that can be properly 
assigned to this genus. In this specimen, it is true, a small alveolus on one 
side contains a small crown of a second incisor, but, on the opposite side, the 
coiTesponding one is shallow and empty. As the last molar is not fully pro¬ 
truded, it would appear that this incisor is a temporary tooth, being removed 
before the maturity of the animal. It thus differs from the existing Camels 
only in the longer persistence of these transitory incisors. The position of 
the first incisor, in the specimen in question, is marked by a roughness of 
the surface, which indicates the still earlier removal of a tooth, and filling 
up of the alveolus. In the P. heterodontus, of which the superior dentition 
of an adult is in my possession, the alveoli of the three superior incisors are 
large and deep, showing that the dental formula is I. |; C. ^; Pm. |; M. 
The alveoli are empty in the specimen, but this is doubtless due to their 
regular funnel-shape, which gives little hold for the conic, though elongate 
fangs. This animal, then, represents a genus distinct from Procamelus, de¬ 
fined by the dental formula just given, for which I have proposed the name 
of Protolabis* The typical and only known species is Protolabis heterodon¬ 
tus, Cope, from the Loup Fork beds of Northeast Colorado. 
* Proc. Acad. Phila. 1876, p. 145. 
