388 
On the Jaw of the Diprotodon Australis. 
From the imperfect development of the teeth, and the sharp¬ 
ness of the transverse ridges of enamel, which exhibit but slight 
indications of wear, it would appear that the individual was a 
young animal. The condyle, coronoid, and angular processes 
are broken off, but the entire body of the jaw remains, with an 
incisor and four molars in situ; completing the number of teeth 
which the jaw at the age of the specimen was capable of con¬ 
taining. 
The alveolus of the incisor extends beneath, and slightly to the 
inside of the first and second molars, the inner wall of the jaw 
being slightly dilated to give room to the fang and pulp of this 
great tooth. About half an inch from the orifice of the socket 
of the incisive tusk the first molar is implanted by two fangs, half 
an inch long; this tooth is one-fourth the size of the next molar, 
and its two transverse ridges instead of running nearly parallel, 
as in the other molar teeth, converge, and very nearly touch at 
the lingual side of the tooth : the talons at the base of the trans¬ 
verse ridges are very small, the anterior one being almost imper¬ 
ceptible. 
The second molar is four times the size of the first, and its 
transverse ridges and talons are well marked; its place in the 
jaw is to the outside, and opposite the termination of the deep 
socket of the incisor tooth. 
The second, third, and fourth molars are well marked, and in¬ 
crease progressively from before backwards, the last being eight 
times larger than the first, and was evidently only in process of 
development when the animal died ; and in all probability had not 
pierced the gum. The fangs are wanting, the dentine had not 
been secreted, and the pulp cavity, formed by two hollow wedges 
of crusta and enamel, alone remains. 
As the plane of the grinding surfaces of the molar teeth forms 
a very acute angle with the base of the jaw, the anterior molars 
would be worn to a considerable extent before the posterior could 
be used. 
The dental formula of the Diprotodon is probably— 
Incisors 1, canines 1, molars !rd_on 
2 0 4—4 A ' v/ * 
Melbourne, Nov. 30, 1847. 
