214 
PROFESSOR OWEN ON THE FOSSIL MAMMALS OF AUSTRALIA. 
To my statement, “ that there is a socket close to the symphysis of the lower jaw of 
Tliylacoleo , which indicates that the canine may have terminated the dental series there, 
and afforded an additional feature of resemblance to the Plagiaulax" * * , Dr. Falconer 
remarks : — “ In all this, it will be seen, the argument is within the domain of conjecture ; 
the tooth oscillates between canine and incisor ; and not merely so, but the principles 
which are followed as guides in this walk of investigation are set aside, to give place to 
the illusory indications of mutilated external form If palaeontological investigations 
were conducted in this manner there would be no limit to conjecture; the landmarks 
we profess to follow would be disregarded, and disorder would face us everywhere. But, 
happily, science furnishes unerring principles, which provide the corrective. I need 
hardly add that the argument drawn from Tliylacoleo has, in my view, no bearing on the 
incisors of Plagiaulax , and gives no support to the carnivorous inference ”f. 
This rebuke, being doubtless kindly meant and penned in the interests of palaeontology, 
I have hitherto borne in silence, hoping that less fragmentary fossils of Tliylacoleo would 
ultimately reach me ; and sustained, I must own, by a confident belief that they would 
confirm the inferences drawn from the position of the alveolus, suggesting the alleged 
feature of resemblance of Tliylacoleo to Plagiaulax. 
Nevertheless, the portion of mandible figured in Plates xi. & xm. of the Phil. Trans, 
for 1859 being represented by a plaster cast, and the figures 5 & 6 in Plate iv. of the 
Phil. Trans, for 1866 being from photographs, I could not feel surprised that arguments 
in favour of the herbivorous nature and affinities of both Tliylacoleo and Plagiaulax 
should have met with acceptance and support from some Anatomists, Naturalists, and 
Palaeontologists 
I have again been favoured, through the kind offices of Sir Daniel Cooper, Bart., 
with a collection of fossils obtained by his friend, Mr. St. Jean, of Gowrie, from the 
freshwater deposits of that locality, in Darling Downs, Queensland, Australia, which 
collection included the alveolar portion and certain teeth of the right upper jaw 
(Plate XI. figs. 1-5), and the major part of the left ramus of the lower jaw with certain 
teeth (Plate XII. figs. 1-5) of a full-grown Tliylacoleo carnifex. 
The teeth in the upper jaw are: — the anterior incisor with the terminal half of the 
crown broken away (i i), the carnassial (p 4 ), and three antecedent small and simple 
obtusely conical teeth (p n 2 > 3 )- 
and Notes,’ by the late Hugh Falconer, F.R.S. &c., 8vo, 1868, vol. ii. p. 437. [In future references I shall 
use the numbers X. and XI. to signify the above volumes.] 
* Owen’s ‘ Paleontology,’ 8vo, 2nd ed. (1861) p. 432. 
t X. p. 354; XI. p. 438. 
J E. g. Mr. Boyd Dawkins, F.R.S., in Quarterly Journal of the Geological Society of London, vol. xx. 1864, 
p. 412 ; Mr. Gerard Krefft, “ On the Dentition of Tliylacoleo carnifex, Owen,” Annals and Magazine of Natural 
History, 3rd series, vol. xviii. 1866, p. 148 ; Professor W. H. Flower, F.R.S., “ On the Affinities and probable 
Habits of the extinct Australian Marsupial, Tliylacoleo carnifex, Owen,” in Quarterly Journal of the Geological 
Society of London, March 1868, vol. xxiv. p. 307. [This volume and paper I shall refer to as No. XII.] 
