BY C. W. DE VIS. 
107 
Form. 
Mandibular. — P. 4 (PI. xvu. fig. G) as it appears in a worn con- 
dition is elongate with mesial diameters 178: 56, oblong tectiform, 
obtusely pointed in front and not dilated posteriorly. Crest 
central, nearly level, obtusely serrated. The mesial two-thirds of 
the crown compressed, but more deeply on the outer side, the 
surface of which has corrugations with much fainter ribs in the 
intervals; the inner surface similarly corrugated. Anterior cusp 
distinctly de lined by the mesial compression, its point low and 
obtuse. Over the intero-posterior angle the crown is more tumid 
than over the outer angle. 
The tooth varies much in proportions and other respects. The 
diameters may become 161 : 72 and the intero-posterior part of the 
crown so tumid as to cause the inner surface of the crown to be 
concave longitudinally, the tooth being then distinctly broader at 
its hinder end. The number, strength and disposition of the 
corrugations are all subject to variation, and frequentty under 
stress of wear disappear altogether. 
P. 3 (PL xvn. fig. 5) in its maiden state is irregularly oblong, 
with mesial diameters 103 : 51; its basal contour is arched on the 
outer side, nearly straight on the inner, its fore end obtusely 
pointed. Crest with five low obtuse cusps, subcentral, curving on 
to the intero-posterior angle, which is sufficiently tumid to render 
the crown vertically concave on that side. Crown compressed, 
with three ribs on the outer and two on tbe inner side, the outer 
ribs graduated in length posteriorly. Anterior cusp moderately 
distinct. 
This tooth also varies in shape, proportions and corrugation. 
The intero-posterior angle may dilate sufficiently to render the 
general form subtriangular, the mesial diameters may vary to 106 : 
66, 89 : 86, the ribs maybe fewer in number or become indefinite. 
Under wear the ribs quickly vanish. 
Molars. — (PI. xvn. fig. 9). The longitudinal linking ridges are 
weak, the lobes but lightly convex posteriorly. Posterior 
basal talons are generally present as erect plates, raised rims or a 
