i 
Cope.] i8 [April 7, 
In the light colored specimen the outer face is wide and nearly plane, the 
anterior very slightly convex, and the posterior concave, making an open 
longitudinal groove ; the external angle is obtuse. In the black speci- 
men the inner face is narrower, the anterior more distinctly convex, and 
the posterior convex also, rounding off to the more obtuse external angle. 
Both these teeth are worn obliquely as in A. jeffersonit. 
The wearing of the median molars is transverse to the axis of the shaft 
anteriorly, oblique to it or descending inwards, posteriorly. The wearing 
in the long axis of the jaw bone, is obliquely forwards on the posterior 
dentinal wall, and divided on the anterior, one half sloping forwards and 
the other backwards, the slopes separated by a sharp ridge of the dentine. 
A. single tooth, which by its form is excluded from a place in the man- 
dible, and by the character of the wearing of its crown, can be none other 
than the second molar, or first of the regular series. Its form is very 
different from that of the same tooth in I. jeffersonit, but is appropriate 
to the modification described below. as characteristic of the inferior 
molars of MW. wheatley?. There is no anterior wear on the anterior den- 
tinal plate, indicating the absence of any tooth anterior to it in the infe- 
rior jaw ; this plate is much higher than the posterior, which has two 
worn surfaces, the anterior horizontal, the posterior oblique. The middle 
of the crown is concave, and the concavity is carried across the dentine 
of one end. ‘The tooth is in section a transverse parallelogram with 
the outer short side oblique, instead of parallel to the inner. Anterior 
face slightly concave, posterior slightly convex. 
The characters of the inferior molars are established by three posterior 
in place in the fragments of jaw held together by the matrix of red sand 
and clay. That they might be the superior series of another species is 
suggested by the subtriangular outline of two of them, and the jawis so 
fragmentary that it is not sufficient to decide the case. The following 
points, however, are conclusive. If they were superior, the terminal 
teeth must be either the second or fifth molars, according to the relation 
to front or back in which they are viewed. ‘That neither can occupy 
this place is proven by the following description: 
The anterior is a rather narrow transverse parallelogram, with the 
sides and angles rounded. The posterior dentinal plate is worn trans- 
versely, the opposite one is oblique, descending to one side. The form is 
worn obliquely away from the centre of the crown, the latter is plane. 
The next tooth is a parallelogram narrowed towards one end, which is 
rounded obliquely to the other sides; it is narrower than the last, and 
the dentinal plates are worn in exactly the same way. The last tooth is 
much wider than the others, and has a subtriangular outline, the narrow 
end very wide and obtuse, and on the same side as the narrowed end of 
the one in front of it. The outline is worn in the same manner, except 
that the angle at one end of the base of the triangle is, perhaps, more 
elevated. 
(1.) Neither of the extremital teeth have the oblique face of the pos- 
ae 
