328 
AKTlODAOTYLxV. 
Procamelus gracilis, Leidy. 
Proc. Acad. Pbila., 1858, 89; Exiiuct Mammalia Dakota and Nebraska, 1869, p. 155. 
An imperfect mandible, with the symphyseal portion complete, sup¬ 
porting several incisors and canines, and the bases of the first four molars, 
represents the smallest species of the genus known to me, which is probably 
the P. gracilis of I^eidy. I give measurements of the fragment: 
Measurements. 
M. 
Length of the jaw to the end of the fourth molar.. 0.127 
Length of the symphysis. 0. 053 
Length to the base of the canine .... 0. 020 
Length to the first premolar. . 0. 044 
Length to the second premolar .. . 0. 076 
Length to the first true molar . 0.108 
Depth of the ramus at the first true molar.. 0. 033 
Depth of the ramus at the second diastema.. . . 0. 023 
The canine tooth rises close behind the external incisor, and the mental 
foramen is below the first premolar. 
the true molars are considerably smaller. The crowns of the latter are stout, and not 
narrowed, nor furnished witii an antero-external ridge, as in P. angustidens, and the 
anterior external crescent projects free posteriorly in an oblique angular rib ou the 
external face of the crown, being separated from the second crescent by a deep fissure. 
The last inferior molar is not very elongate, and the fifth lobe has a crescentic section, 
i. e., is concave on the external face, as in the P. angustidens. 
The inferior border of the ramus is straight from the first true molar posteriorly. 
The anterior face of the coronoid process is oblique outward. The edge of the masse¬ 
teric insertion forms a low ridge, concentric with the convex posterior border of the 
jaw. Like the inner face of the same portion of the jaw, the surface is flat. 
Measurements. 
P. fissidens. P. oecidentalis. 
M. M. 
Length of the entire molar series. 0.112 0.126 
Length of the premolars. 0.0385 0.042 
Length of the second true molor. 0.023 0.0275 
Width of the same.-•. 0. 015 0.0165 
Length of the third true molar... 0.033 0.036 
Width of the same. 0.014 0.014 
Depth of the ramus at the first true molar.. 0.035 . 
Depth of the ramus at the middle of the last molar. 0.040 0. 051 
Depth of the ramus at the apex of the coronoid process. 0.140 . 
Depth of the ramus at the condyle.. 0.108 0.118 
Depth of the ramus at the jyostcondylar angle. 0.069 0.085 
One ramus nearly entire and the molars of another (excepting the last) were 
obtained near the Pawnee Buttes of Northeastern Colorado. 
