544 ON DIPROTODON 
form of a cone than that of a crest, is not more than half as broad as: 
the others, and terminates, internally, in a smoothly rounded convex 
pillar, which remains distinct to the base of the crown. From its 
anterior surface a ridge springs, which, gradually decreasing in 
height, skirts its base and then ascends, upon the inner part of the 
middle ridge, to form the anterior boundary of the inner face of the 
tooth. The posterior basal ridge is well marked and concave up- 
wards ; its inner and outer ends, as it were, ascending upon the 
postero-external and postero-internal angles of the tooth. The 
anterior, or mammillary, elevation is not at all worn in either 
tooth. The middle and posterior ridges are slightly worn, so as to 
give rise to two elongated facets, each not more than one-sixth of an 
inch wide, and passing into one another internally, being separated 
only by the posterior groove, which dilates somewhat suddenly at its 
inner end (fig. 2). 
The premolar of No. 2 is constructed upon precisely the same 
general plan as that of No. 1, but differs in several details. Thus, 
it is slightly smaller, and the antero-internal ridge which skirts the 
base of the mammilla has a somewhat different form. But the 
most marked difference is offered by the outer surface of the tooth 
(fig. 4), which presents not merely three smoothly convex surfaces, as 
in the other specimen, but exhibits three well-defined vertical ridges, 
connected by prominent, curved, basal elevations. The premolar of 
this specimen is altogether somewhat smaller than that of the other. 
That both these specimens are specifically distinct from the only 
species of Dzprotedon known at present, viz. D. australis, appears 
likely, at first sight, from a comparison of the dimensions of the 
corresponding teeth. 
In the maxilla of Dzprotodon australis (British Museum, No. 
32848), to which I have already referred, the socket of the premolar 
and the first and second molars occupy a space of 4} inches in the 
alveolar margin of the maxilla: in No. 2 the same teeth occupy 
only about 34 inches. The measurements of the individual teeth, 
given in eighths of an inch in the following table, present a nearly 
similar ratio. 
No. 2. ( No. 1. l D. australis (B.M). 
Breadth. Length. | Breadth. Length. Breadth. — Length. 
Premolar cacsccrnacnarie 64 74 1 7 8 5 g1 
First Molar yacesscaran. 94 ite) | 12 if) 13 12 
Second molar......... 11g 12 oe se 16 15 
Fourth molar ......... 13 16 | 17 20 
1 These are measurements of the alveolus and its contained fang. The crown of the 
tooth was doubtless much larger in each dimension. 
