314 MEMOIRS OF THE CARNEGIE MUSEUM 
is entirely surrounded by a heavy cingulum. The enamel is smooth. P* is wider 
than long, as in Thinohyus pristinus Cope. The triturating surface of the tooth is 
worn down, but indicates a single external cusp, the protocone. The deuterocone 
is also strongly developed, and there are heavy anterior and posterior cingula. There 
is an external cingulum, while the tooth is smooth on its internal side. 
The first and second superior true molars are much worn. ‘The grinding surface 
of the former is in its worn condition a large basin surrounded by heavy enamel. 
The cones are entirely obliterated, but the external remnant of the transverse valley 
indicates a quadritubercular crown. The cingulum on the postero-external lobe is 
present, while that on the antero-external lobe is wanting. The internal face has 
no cingulum. M?° has strong external and internal remnants of the transverse 
valley, extending well in on the triturating surface presenting nearly an antero-pos- 
terior 8-shaped basin. There is an anterior and posterior cingulum. Externally 
the cingulum is weakly developed and internally the tooth is smooth. M2? has the 
greatest antero-posterior diameter of all the teeth in the upper jaw. ‘Phe para- and 
protocones of m® are well worn, but indicate that they were well separated and of 
considerable size, especially the paracone. ‘The meta- and hypocones are of smaller 
size and are closer together. The abrasion on this tooth indicates the former pres- 
ence of a metaconule. The anterior half of the grinding face is too much worn to 
justify the statement that a protoconule was present. ‘There is a heavy anterior 
cingulum and a strong posterior heel. There is no internal cingulum, while the 
external is faint. The tooth is broadest anteriorly and tapers rapidly on the exter- 
nal face from the paracone to the evenly rounded heel. The internal border is an 
almost straight antero-posterior line. 
INFERIOR DENTITION. 
Puate XXXIV. 
All the incisors of the lower jaw and also the canine on the left side are want- 
ing. |The right canine is present, but with the top broken off. This is a heavy and 
almost vertically placed tooth, very deeply imbedded in the mandible. Its antero- 
posterior diameter is greater than the transverse. There are shallow grooves on the 
tooth, one on the internal and one on the external face. The anterior border is 
narrow and evenly rounded, while the posterior border is broad and more angular, 
thus presenting a sub-triangular cross-section. There is a deep oblique abrasion on 
the posterior face caused by friction with the superior canine. P, is absent. There 
is a long diastema from the canine to py. The latter is in a continuous series with 
