PEOFESSOE OWEN ON THE FOSSIL MAMMALS OF AUSTEALIA. 
227 
ridges, in which the serrate or finely undulated or wrinkled character is more or less 
manifest, especially on the trenchant anterior border, defining the outer (fig. 5) from the 
inner (figs. 4 & 6, i ) surfaces of the crown, also on the supplementary ridge ( d ) on the 
inner facet (i). 
As the fore-and-aft breadth of the crown increases from the apex downward, the 
stronger convexity of the antero-external part is limited to the fore part of that facet, 
the hinder part of the facet becoming less convex or almost flattened, and at the base 
of the crown even feebly concave, where the cement (fig. 5, c) encroaches on the enamel. 
A similar concavity marks the outer part of the base of the laniariform incisor of Pla- 
giaulax, Falconer, X. fig. 1, p. 366 ; XI. pi. 33. fig. 1, a. The anterior subserrate 
ridge is the longest, the postexternal ridge subsides a little sooner in approaching the 
base, the postinternal ridge is next in length, and the supplementary inner ridge is the 
shortest. The enamel-case of the crown is entire, but is thickest upon the more convex 
anterior part of the antero-external facet, and where it forms the ridges (see the section, 
Plate XIII. fig. 8). 
The posterior facet at the apical part of the crown meets at a right angle the inner 
side, but lower down it slopes from the postinternal ridge, backward as well as outward, 
to meet the outer facet at b. This gives a more trenchant character to the subserrate 
ridge or border (d) between these surfaces. 
The effective cutting power of the postinternal ridge, where the angle between the 
posterior and internal surfaces of this three-sided bayonet-like tooth becomes a little 
open, is enhanced by the prominence of the ridge, supplemental strength being given 
to the piercer by the added postinternal ridge. The cement-clad root (Plate XIII. 
figs. 5, 6 & 7, c,f) gradually contracts to its subtruncate closed extremity. 
In the specimens of lower laniary above described, as in the cast and photographs of 
that formidable tooth of Thylacoleo , evidence is given of its conforming in its limited or 
temporary growth, as in its shape, proportions, and structure, with the canine of the 
Felines, but with superadded modifications strengthening and perfecting it for its work 
as a piercer, holder, and lacerator. 
§ 7. Guide to inferring function from form of Teeth. — Thus, through the coopera- 
tion of a liberal and enlightened Legislature and Administration, and of esteemed friends 
and fellow-labourers in Sydney, New South Wales, ample evidence has been got of both 
upper and lower laniary incisors, as well as of the rest of the dentition of Thylacoleo 
carnifex. 
It is with pleasure, though without surprise, that I have been enabled to confirm the 
inferences expressed in my former papers, on such elements of that dentition as I then 
only knew “ in part.” 
Whether the “ principles which are followed as guides in this walk of investigation 
were” therein “ set aside, to give place to the illusory indications of mutilated external 
form”*, I cannot determine, because Dr. Falconer does not define the principles to which 
* X. p. 354 ; XI. p. 437. 
