56 
PROFESSOR OWEN ON THE FOSSIL MAMMALS OF AUSTRALIA. 
At the upper part of the symphysis the ridge (fig. 3, k), of which the beginning or 
hind part was noted in the description of the preceding specimen (Plate IV. figs. 1 & 4, k), 
is here seen to converge toward its fellow for the extent of an inch, then to be con- 
tinued straight forward, broadening and subsiding. The pair of ridges form the sides 
of the smooth channel (s*), grooving the upper surface of the symphysis, and gradually 
shallowing to the fore end. Posteriorly the channel rapidly widens to the intermolar 
space, then gradually expands, preserving or gaining depth to the hind border of the 
symphysis (s'). The entire length of this confluent tract of the mandibular rami is 
5 inches 10 lines; the thick rounded hind border is on the vertical parallel with the 
hind lobe of the third molar (m i). It is satisfactory to find this character of the former 
mandible of Nototherium Mitclielli (Plate IV. fig. 2, s) here repeated. The under part 
of the hind end of the symphysis shows the insertional depressed surface (Plate V. 
fig. 2, v, v , of similar size and shape to that in the subject of Plate IV. fig. 3, v). The 
symphysis is subcompressed anterior to the molars, but the transverse diameter dimi- 
nishes less gradually than the vertical one. 
The present mandible is of a full-grown and, from the wear of the teeth, rather aged 
individual. The last three molars and a portion of the second are in place in the right 
ramus : the first, second, and part of the third molars remain in so much as is preserved 
of the left ramus. 
The fore-and-aft extent of the molar alveoli is 6 inches 10 lines; that of the three 
hindmost is 5 inches 2 lines. I give this measurement, as well as the first, to show the 
close correspondence in size of the present with the preceding mandible of Not other iurn : 
the present specimen is rather smaller ; the bone is rather more slender ; the vertical 
diameter, for example, of the ramus anterior to the foremost molar-socket is 2 inches 
4 lines, in the subject of Plate IV. it is 3 inches; the vertical diameter behind the 
socket of the last molar in the subject of Plate V. is 2 inches 10 lines, in that of 
Plate IV. it is 3 inches 9 lines, in the type jaw f it is 3 inches 8 lines. With the closer 
conformity in the molar series, I infer the more slender proportions of the present man- 
dible to be sexual, and to indicate its having come from a female Notothere. 
Pather more of the base of the coronoid process (Plate V. figs. 1 & 3, q, o) is here 
preserved than in the subject of Plate IV. ; it occupies the same proportion, and shows 
the same shape and curve as in that jaw; the dental canal perforates its hind part in 
the same position and with the same obliquity. The postalveolar process, broken as in 
the former mandible, and as it usually is in these Australian fluviatile fossils, holds 
the same relative position to the last molar tooth as in the male jaw. The smooth 
oblique channel between the fore part of the coronoid and the last alveolus has a breadth 
of 9 lines in the female, instead of 12 lines as in the male specimen. The anterior 
inflected angular border repeats the characters of the part in that specimen, but is not 
entire ; the exceptionally perfect condition of the part in the type mandible J gives con- 
sequently valuable evidence of this character, 
t Loc. cit. ; and Cut, fig. 1 
t Loc. cit . ; and Cut, fig. 1, d. 
