MESODONTA. 
14U 
the other is much larger than any of the allies, approacliing the larger spe¬ 
cies of Ryracotherium. 
Sarcolemur mentalis, Cope. 
Plate xlv, fig. 15. 
Antiacodon tnentalis, Cope, System. Cat. Vert. New Mexico, U. S. Geog. Survs. W. of 
100th M., 1875, p. 17. 
Established on a portion of a ramus mandibuli, on which the first and 
second true molars only remain. The fangs of the last premolar are stout, 
and evidently supported a robust crown. The cusps of the true molars are 
as usual, crescentic in section on the outer side, the posterior inner conic, 
while the double anterior inner is rounded on the internal face, and not 
flattened, as in many species. The second true molar has a distinct poste¬ 
rior median tubercle. There are no basal cingula except a trace between 
the external cusps. This species resembles the A. furcatus, but differs 
materially from it, as from A. pygmceus, in the deeper and more robust 
mandibular bone. 
Measurements. 
Length of the first true molar. 
Width of the first true molar behind. 
Depth of the ramus at front of the third molar .. 
Depth of the ramus at front of the last premolar, 
S. mentalis. S. i)ygmwus. 
M. M. 
0. 0044 0. 0043 
0.0033 0.0031 
0.0085 0. 0075 
0.0078 0.0055 
Sarcolemur crassus, Cope. 
Plate xlv, fig. 16. 
Antiacodon crassus, Cope, System. Cat. Vert. New Mexico, U. S. Geog. Survs. W. of 
100th M., 1875, p. 57. 
Represented by a portion of the right mandibular ramus, which sup¬ 
ports the first and second true molars. It is a peculiar species, known 
among its allies by the obtuseness of the cusps and ridges of the crown. 
The double cusp is thick, and the component apices little separated; the 
anterior only is connected with the external anterior tubercle. The poste¬ 
rior part of the crown is wider than the anterior, and is quite concave. The 
outer border supports a stout tubercle; the inner, a very small one behind, 
and there is a small ledge representing the posterior median. The oblique 
ridge from the posterior external cusp is low, and the anterior cusps rise 
