164 
T^mODONTA. 
in section. The second tooth is peculiar, and having its transverse diameter 
twice as great as the antero-posterior, its position in the jaw is thus 
transverse. The root is like that of the other teeth, simple, but is slightly 
constricted on both the wide faces at the middle; its position near the 
ascent of the large incisor causes it to be a little shorter than that of some 
of the others. The first mandibular tooth is small; its alveolus is triangular- 
oval in section, the longer and oblique side being internal, and extending 
alongside of the large incisor three-quarters of its length. It is possible 
that this tooth should be reckoned as an incisor. f 
A well-preserved molar contracts downward to the base of the root, 
which is not twice as long as the crown. The latter has perpendicular 
sides, and one of its diameters is a little longer than the other. The enamel 
investment of the crown is uninterrupted on the sid^s, but has an irregular 
line of contact with the superficial layer of the root. If the side where 
the enamel descends lowest, be, according to the analogy of other species, 
the external, the boundary on the inner side is a little higher and oblique; 
it is angulate on the narrower end, and deeply notched at the wider end. 
The former will be, according to the analogy of other species, the anterior. 
It supports a transverse yoke, partly divided into two tubercles, whose long 
axis is also transverse. The posterior end of the crown supports two much 
smaller tubercles, which form the central part of a crescentic elevation of 
the border of the crown. One apex of this crescent is separated from the 
anterior yoke by a deep fissure; the other apex is contracted within the 
border of the crown, and, descending, extends to the basis of the anterior 
yoke, resembling the oblique yoke of the inferior molars of JEctoganus and 
Estliomjx. Center of the crown concave; no cingula, except a trace at the 
middle base of the anterior yoke. Enamel smooth. Fragments of incisor 
teeth accompanying this jaw exhibit smooth enamel, without longitudinal 
grooves or striae, and without transverse lines of growth or rugosities of 
any kind; the section of this face is uniformly convex. A portion of the 
middle of the incisor in the jaw shows a shallow longitudinal groove near 
the posterior external margin. Tlie incisive alveolus extends to below the 
third molar from behind. 
