412 ON A NEW SPECIES OF MACRAUCHENIA (M. BOLIVIENSIS) 
like the preceding, its face shelves upwards and inwards. The poste- 
rior part of its outer margin is broken away ; but it is clear that this 
crown was quite as wide as that which preceded it, if not wider ; 
the surface appears, however, to have been more evenly flat. The 
inner perpendicular face of the impression presents two concavities, 
separated by a slight ridge. 
More of this tooth is preserved than of any other; the outer wall 
of the maxilla is, for the most part, preserved over it, and encloses the 
alveoli of two external fangs. There is evidently at least one, and 
perhaps two, internal fangs. The whole thickness of the inner and 
posterior part of the crown is preserved, and the posterior and inner 
half of its worn face; the rest of the tooth is broken away. The 
posterior and outer fang, partially exposed, is 0-3 of an inch long, 
conical, and slightly inclined backwards, as well as upwards and 
inwards. The crown, where it joins the fang, is o'4 of an inch long; 
so that it must have widened a little below. The vertical height of 
the crown of the tooth posteriorly and internally is hardly more than 
O'15; anteriorly and internally it is broken; but, when entire, it had 
a height of at least o'2. The inner surface of the tooth is divided 
into two tolerably well-marked subcylindrical faces, which correspond 
with the impressions on the inner wall of the coronal impressions. 
The outer moiety of the crown is altogether broken away; the 
inner moiety, broken anteriorly, exhibits in its posterior half a 
smoothly worn facet, concave from before backwards, and inclined 
not only downwards but slightly backwards. A narrow fringe of 
enamel appears to surround the worn dentine of this face, which is 
wider in the middle than at the two ends. The true outer face of the 
enamel can be traced from the inner face of the tooth, continuously, 
round the posterior boundary of this worn facet, and as far as its 
most dilated portion on the inner side. It is concave outwards, and 
presents a slight inflexion midway between the posterior end of the 
facet and its middle dilatation. Beyond the dilated middle of the 
facet, its enamel-wall seems to have been united with that of the 
opposite half of the tooth; but it is traceable forwards, becoming 
concave externally, past the anterior end of the worn facet, to the 
anterior margin of the tooth, where it bends round, and again becomes 
continuous with the enamel of the inner face. 
This tooth, therefore, appears to have possessed an internal 
division, elongated from before backwards, surrounded by a narrow 
band of enamel—having its inner contour produced into two con- 
vexities, separated by a slight vertical depression, while its outer wall 
presents two concavities, separated by a slight ridge which lies rather 
