50 AMPHITHERIID®. 
figure, four times enlarged, the condyle and angle of the 
jaw have been left out for want of room in the page, but 
their shape is accurately given in the outline above. 
In this specimen the whole of the exposed surface of the 
left ramus of the lower jaw, with the exception of the 
coronoid, articular, and angular processes, is entire; the 
smooth surface near the anterior extremity of the jaw is in 
bold relief, and slopes away at nearly a right angle from 
the rougher articular surface of the elongated symphysis. 
It may be supposed that this symphysial surface, which 
at once determines the side of the jaw, might be obscured 
in the plaster cast studied by M. de Blainville, who has 
contended, in opposition to the opinion of M. Valenciennes, 
that the outside of the jaw was here displayed, but there is 
no possibility of mistaking it in the fossil itself; it is long 
and narrow, and is continued forwards in the same line 
with the gently convex inferior margin of the jaw, which 
thus tapers gradually to a pointed anterior extremity, 
precisely as in the jaws of the Didelphys as well as in other 
Insectivora, both of the marsupial and placental series. Its 
lower margin presents a small but pretty deep notch, (f,) 
which possesses every appearance of a natural structure, 
and a corresponding but shallower notch, is present in the 
same part of the jaw of the W/yrmecobius. In the relative 
length of the symphysis, as in its form and position, the 
jaw of the Amphitherium corresponds with that of the 
Didelphys, Myrmecobius, and Gymnurus. A greater pro- 
portion of the convex articular condyle is preserved in this 
than in the foregoing specimen, and it projects backward 
to a greater extent. The precise contour of the coronoid 
process is not so neatly defined in this as in the first 
specimen of Amphitherium, but sufficient remains to show 
that it had the same height and width. 
