ON A NEW.SPECIES OF MACRAUCHENIA (M. BOLIVIENSIS) 413 
behind the level of the depression on the inner face. By use, the 
posterior part of this division wore down into a facet, concave from 
before backwards, and separated, by a transverse ridge, from the facet 
in front of it. A longitudinal fossa separated the posterior moiety, at 
least, of this division of the tooth, from the outer division. 
Imperfect as is this fragmentary grinder, certain important con- 
clusions may, | conceive, be very safely drawn from its structure. 
The predominance of the longitudinal, to the exclusion of transverse 
valleys and ridges in the crown of the tooth, the distinct, though 
not strongly marked, crescentic form of the internal division of the 
tooth, and its short crown, remove it from the teeth of any known 
Perissodactyle Mammal, and lead one, at once, to seek its analogue 
among the Artiodactyla; and of these the Ruminants alone, so far 
as I know, offer anything like it. The inner grinding-surface of 
any true molar of a Ruminant, however, exhibits two ridges and 
three depressions, while that of the A/acrauchenia has only one ridge, 
with a concave shelving depression behind, and doubtless, in the 
perfect condition, another in front; in other words, it has the con- 
tour exhibited by one of the hinder premolars of a Ruminant. The 
inner division of a posterior premolar of Azchenta has its convex 
inner surface undivided by any vertical depression ; and its outer 
posterior margin exhibits no marked inflexion: but such an inflexion 
exists in the corresponding teeth of the Giraffe and of many Deer, in 
some of which latter a vertical groove, dividing the inner face into 
two convexities, may also be noted. 
I am of opinion, therefore, that the tooth in question is a posterior 
premolar, and that it was constructed upon the Ruminant type. In 
this case, however, the dentition of MWacrauchenta must have departed 
widely from that of the Came/id@ ; for there were certainly two teeth 
with flat grinding crowns in front of that just described, which would 
give, at least, three premolars in all, or as many as are found in 
ordinary Ruminants. 
I am strengthened in the conviction that there were as many as 
three premolars, by the rest of the structure of this interesting frag- 
ment. Within the series of teeth just described, in fact, it presents 
a considerable portion of the roof of the palate, some of whose bony 
matter remains. At a distance of half an inch from the inner wall 
of the posterior premolar, a longitudinal sutural line traverses the 
whole length of the palatine surface, and ends abruptly (in conse- 
quence of the fracture of the matrix) as well behind as in front, 
Its posterior end is 12 of an inch behind a transverse line drawn at 
the level of the posterior margin of the last premolar. Opposite and 
