358 PEOFBSSOK OWEN ON TKE SPECIES OF PHASCOLOMYS. 



which contained the generalized expression of observations on the dentition and other 

 systems, carried out through all the materials then at my command. This was chiefly 

 in relation to the actual phase of Mammalian taxonomy in reference to Cuvier's order 

 "Marsupiaux"'. W. S. Macleay and others opposed such ordinal group or union of 

 the pouched quadrupeds. The learned Vice-Secretary of the Zoological Society had 

 published reasons for rejecting the Marsupialia as a distinct group, and for distributing 

 them among different placental orders according to their supposed closer affinities. The 

 contrary views set forth by Cuvier and De Blainville'' were defective in that kind of evi- 

 dence which could alone render them convincing ; accordingly Mr. Bennett asks, in 

 1831, " What is there of importance in the structure of the Wombat, except this solitary 

 character of the marsupium, to separate it from the Rodent order f. " 



Amongst the structures shown to be both common and peculiar to the Marsupialia, I 

 adduced the number of the true molar teeth, as characterized by size and shape, 

 remarking that " in the dental system itself, the varieties of which have been chiefly 

 appealed to as sanctioning the dispartition of the Marsupial order, we find an important 

 peculiarity, by which the carnivorous, omnivorous, and strictly vegetable-feeding genera 

 ahke agree with each other, and differ from the corresponding placental Mammalia. 

 In the ordinary Ferce, for example, in the Quadrumana and in the Bodentia, as like- 

 wise in the Fachydermata and Ruminantia, the number of grinders developed on each 

 side of each jaw, which are not subject to vertical displacement and succession, is never 

 more than three, while in the corresponding groups oi Marsupialia it is always ybwr'". 



Since the date of this paper (1839) the associated group of Marsupialia has not been 

 sought to be dissevered. It received the valuable sanction of Mr. Waterhouse in his 

 ' Natural History of the Mammalia;' and the generalization as to the number of true 

 molars is given amongst the characters of the order in Part I. of that work, which was 

 issued in 1845. 



' Eegne Animal, vol. i. p. 172 (ed. 1829). 



- Although De BlalnviUe was able to anticipate the appearance of the concluding volume of the ' Eegne 

 Animal,' by a few months, in the issue of his Tabular Sheets of Classification, the priority of the proposition of 

 a Marsupial series distinct from, but paralleling, the higher Mammalian orders, is due to Cuvier (" Preface 

 de la premiere edition, Ootobre 1816"). 



' Trans. Zool. Soc. vol. ii. p. 332. I noted here the exception, previously pointed out by Mr. "Waterhouse, 

 in Petav.rus (Acrobates) pyrimmis, also that of the similarly minute Phalaw/ista gliriformis, pp. 325-333. 



