534 
PROFESSOR OWEN ON THE FOSSIL MAMMALS OF AUSTRALIA. 
bed in the “Melbourne district,” described in my 4 Catalogue of Fossils in the Museum 
of the Royal College of Surgeons’ (4to, 1845), p. 308, no. 1491 ; and such trace of socket 
showed the tooth to have been implanted by two fangs. The corresponding divisions of 
the socket of d 3, with the fangs in situ , are better preserved in the specimen figured in 
Plate XLII. fig. 5, and Plate XLIII. figs. 1 & 2, d 3. Dr. Hobson, shortly before his 
death in 1848, transmitted to me a sketch of this tooth in situ , in a fragment of the 
lower jaw of a young Dvprotodon (Cut, fig. 2), according to which the anterior as well 
as the posterior lobe of d 3 is in the form of a transverse 
wedge ; there is a basal ridge along both the fore and hind 
parts of the crown, the latter being the broadest ; in short, 
d 3 presents, in miniature, the bilophodont type of the 
succeeding molars. From the attrition of the two lobes it 
may be inferred that the opposing molar above was also 
transversely two-ridged. That the tooth (fig. 2) answers 
to the one which occupied the socket (d 3) in Plates XLI. 
& XLII. fig. 5, is shown by correspondence of size. The 
fore-and-aft extent of the socket in both is 9 lines, the 
breadth of the division for the anterior fang is 4 lines, of 
that for the posterior fang 44 lines ; the alveolar wall ex- 
tending transversely between the two divisions exceeds a 
line in thickness ; each fang is subcircular at its fractured 
end, with an indent at the side turned toward the other 
fang, indicative of a longitudinal groove into which the _. ; . , 
° . . T irst lower molar, cl 3, young Dvpro- 
walls of the socket enters, giving a firmer implantation to todon, nat. size. 
the tooth. 
In the portion of mandible (Plate XLI. & XLII. fig. 5) the penultimate molar (m 2) 
had not risen completely into place, and the posterior lobe was barely touched by masti- 
catory work. In the mandibular ramus (Plate XLII. fig. 2), with the last molar (m 3) 
in place and both ridges showing wear, the two divisions of the socket of d 3 are retained, 
without trace of tooth. The fore-and-aft extent of the socket is 9 lines, that of the hind 
fossa or division is 3-| lines, that of the front one 24 lines, and that of the intervening 
bar is 24 lines at its prominent part. 
In the younger jaw the second molar (Plate XLI. figs. 1 & 2, d 4) has both lobes of 
the crown about half worn down ; the fore-and-aft extent of the crown, including the 
anterior and posterior basal ridges, is 1 inch 6 lines. The anterior basal ridge is thickest 
at its outer part, and here the enamel has been worn off in mastication. The flat fore 
side of the front lobe rises 5 lines above the ridge. The abraded surface (Plate XL. 
fig. 3, ct) of this lobe is 8 lines in transverse and 4 lines in antero-posterior extent, the 
mid part being increased in this direction by an outswelling of the hind surface there of 
the lobe. The outswelling of the front slope or surface of the hind lobe is situated more 
outwardly : the abraded surface (Plate XL. fig. 3, h) of this lobe is narrower from before 
