PROFESSOR OWEN ON THE FOSSIL MAMMALS OF AUSTRALIA. 
257 
This fact invalidates the averment of “ the contradictory bearing of the dental system 
of Plagiaulax upon the assumption that the earliest Mammals had the full complement 
of teeth which averment Dr. Falconer reiterates and “ calls special attention to,” in X. 
p. 365, XI. p. 451. For if, in place of assuming Plagiaulax to be the earliest mammal, 
and, as such, with the full complement of teeth, or “ the oldest well-ascertained herbi- 
vorous mammal,” it be viewed as no more than it is, viz. a geologically earlier form than 
Thylacoleo with a dentition similarly modified for carnivority, the degree of difference 
between the two members of the Paucidentata is affirmatory instead of contradictory, 
in relation to the rule in question, rightly stated. 
§ 18. Relation of Size to Carnivority. — One other argument against the predatory way 
of life of the subject of the present Paper remains for notice, although its very sugges- 
tion implies a sense of the insecurity of the grounds on which the herbivorous habits 
and affinities of Plagiaulax and Thylacoleo have been advocated. 
They are affirmed to have been animals too small, too feeble, to have preyed upon 
others, especially when much larger than themselves. 
Whoever has witnessed the well-known zoological phenomenon of the pertinacious 
pursuit and fatal attack of a hare by the diminutive weasel would pause, however, be- 
fore venturing on such grounds of objection. 
Dr. Falconer, selecting for his purpose the most diminutive of the species of Plagi- 
aulax, affirms : “ The entire length of the specimen, including the six molars and pre- 
molars, together with the procumbent incisor (according to the metrical line e), does 
not exceed f 4 of an inch, of which the six cheek-teeth united make only about two 
and a half lines ("25 inch). I ask any zoologist or comparative anatomist to look at it, 
and say whether the dental apparatus of this extremely minute creature is competent 
to perform the duties required of a predaceous carnivore. Magnitude in this case is an 
important ingredient, as it necessarily involves measure of force. Could P. minor have 
preyed on small Mammals and Lizards l Is it not more probable that this pigmy form 
was itself an object of prey in the Purbeck fauna'?”'* 
To this I reply, that I have now before me the original of fig. 15, Plagiaulax minor 
of the Quarterly Journal of the Geological Society of London for August 1857, xiii. p. 281, 
reproduced in the subsequent paper of Dr. Falconer in Quarterly Journal &c. for June 
1862 (X. p. 367), and copied in pi. 34. fig. 2 of the posthumous work (XI. p. 416). 
The specimen (fig. 20, a) shows two molars and four premolars ; the incisor is neither 
chisel-shaped nor procumbent, but rises with a slight curve to its pointed apex at an 
angle of 120°, with the line of the molar alveoli. The length of the dental series from 
the apex of the laniariform incisor to the hind part of the second molar is seven-six- 
teenths of an English inch, precisely the length of the dental series in TJrotriclius tal- 
poides (ib. b), a ferine mammal, 5 inches long from the snout to the tip of the tail, with 
a skull 1 inch in length, and an approximate pair of lower pointed incisors upcurved 
at the same angle as in Plagiaulax minor, but relatively less and shorter. 
* X. p. 363 ; XI. p. 448. 
