50 AMPHITHERIID^E. 



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, (/,) 

 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 Myrmecobius. In the relative 

 length of the symphysis, as in its form and position, the 

 jaw of the AmpMtkerium 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. 



