PEKISSODACTYLA. 
257 
A fragment of the left mandibular ramus of another individual supports 
the last two true molars. The last molar has a short heel with dentellated 
margin on the inner side, and oblique ridge connecting it with the external 
cusp adjacent to it. Both molars possess a well-marked external basal 
cingulum, and an oblique ledge descending inward from the external 
anterior cusp. The penultimate molar exhibits a posterior cingulum, which 
presents an angle upward. Enamel slightly wrinkled. 
Measurements. 
M. 
Length of the last inferior molar. —... 0.0110 
Width of the same in front. 0. 0055 
Elevation of the same in front ... 0. 0055 
Length of the penultimate inferior molar. 0. 0080 
Width of the same in front. 0. 0055 
Depth of the ramus at the anterior part of the last molar. 0. 0170 
Orotherium loevii, Cope. 
Plate Ixv, figs. 15-17. 
Represented by a portion of the left mandibular ramus supporting 
three premolars and two true molars, and probably by a similar portion of 
the right ramus which accompanied it, and a portion of the right maxillary 
bone, bearing the second and third premolars, also found with it. These 
fragments belonged to an adult animal of smaller size than either of the 
preceding. The crowns of the molars are so worn as to render it impossible 
to decide on the character of the inner anterior cusp, but the fourth pre¬ 
molar possesses the inner posterior cusp characteristic of the 0. cristonense. 
The fourth premolar has two subequal elevated anterior cusps, with a 
pronounced basal tubercle in front, and no external cingulum. The true 
molars have a well-marked anterior ledge, and posterior median tubercle. 
There is an external cingulum between the cusps, but whether completed 
round the bases of the cusps is not certain from the amount of attrition 
which they have undergone. No trace of cingulum on the inner side; 
enamel smooth. 
The base of the first premolar is a wide triangle with the base posterior. 
It has an internal but no external cingulum; the crown consists of a single 
cusp with an obtuse posterior cutting-lobe. The second premolar possesses 
17 G R 
