62 
PROFESSOR OWEN ON THE FOSSIL MAMMALS OF AUSTRALIA. 
canal runs obliquely forward ; only the two anterior thirds of the orifice are defined by 
a sharp border ; the diameter of the orifice is 4 lines. A groove (fig. 2, p) of the same 
breadth, and about an inch and a half in length, runs forward along the under and inner 
side of the orifice (o) ; this groove has a sharp inner border. A parallel ridge is directed 
from the back part of the dental orifice where it is broadest, backward, becoming nar- 
rower as it recedes, and subsiding an inch and a half from the orifice. 
About 3 inches, following the curve, of the back part of the base of the coronoid (r,f) 
are preserved ; its commencement from the neck of the condyle (r) is raised much above 
the horizontal plane of the molar alveoli : the plate here is thin, but its margin is obtuse 
or rounded ; at the hind part of the fracture (f) it shows a thickness of 2 lines ; as it 
advances it gains one of 3 lines ; as the anterior border descends it gradually increases 
in thickness to 6 lines, near its obtusely rounded basal beginning. This (fig. 1, q ), as 
usual, rises, buttress-like, from the outer wall of the mandible, on the transverse parallel 
of the middle of the last alveolus, and about an inch and a half lower than the outlet 
of that socket. The course of the base of the coronoid upward and backward is with a 
slight outward concavity at its anterior half, and is then level ; its extent is 4 inches 
9 lines; the anterior border of the process is gently convex, to the extent (4 inches) to 
which it has been preserved. The breadth of so much of the condyle (c) as is preserved 
is 2 inches 3 lines ; the outer portion shows a small part of the articular surface, convex 
from before backward. 
The ectocrotaphyte depression (fig. 1 ,f) is smooth and shallow ; it is divided from the 
lower inflected part of the ascending ramus by a change of contour of the smooth outer 
surface, forming a broad convexity vertically ; but this becomes, as it recedes, rather 
more prominent, thinner, and shows a roughened, as it were worm-eaten, surface (fig. 1, h), 
and, from a slight inflection at its termination towards the back surface of the ascending 
ramus, it there indicates the fore-and-aft extent of that part of the jaw as giving, viz. 
from the fore part of the base of the coronoid, 6 inches. It is possible that a smoother 
surface of the hind prominent outer and lower boundary of the ascending ramus may 
have suffered some abrasion in the fossil. There is no perforation of the crotaphyte 
depression. 
The symphysial end of the present ramus has been broken away at the fore part of 
the second alveolus, exposing part of the anterior root of that tooth (fig. 4, d 4 ), and a 
small part of the bottom of the incisor’s socket (?'). 
The antero-posterior extent of the last three molar sockets is 4 inches 10 lines ; a thin 
plate rises to form the outer wall of their outlets. 
The inbending of the inner surface to form the hind part of the symphysis begins at 
the vertical parallel of the middle of the third molar (fig. 2, s, m i ). The lower part 
of the symphysis shows a pair of transversely crescentic insertional depressions, concave 
backward (fig. 3, v, v ). The depth of the ramus at the interval between the third ( m 1 ) 
and fourth (m 2 ) sockets is 2 inches 8 lines : in the female (?) of Notothcriiim Mitclielli 
it is 3 inches ; in the male (?) it may attain 3 inches 10 lines. 
