ON THE ANATOMY OF THE KOALA. 187 



canine and the five molars of the upper jaw, and the incisor and the 

 corresponding teeth in the lower jaw." Dr. Murie, from his examination 

 of the osteology of the Wombats (P. Z. S. 1867, p. 815), appears also to 

 incline to Mr. Waterhouse's view. 



In the course of this paper I have already noted several other points 

 of resemblance between the Koala and Wombat, in the presence in both 

 of more or less distinct cheek-pouches, in the absence of a distinct 

 caudate lobe to the liver and the tendency of its lobes to develop addi- 

 tional superficial sulci, and, finally, in the structure of the female repro- 

 ductive organs. In the Wombat, too, the first traces of the syndactyle 

 condition of the pes appears, both externally and also in the structure of 

 the bones. But, to my mind, the most convincing token of their affinity 

 is their possession of the peculiar gastric gland * already referred to and 

 described. In no other Marsupial is there any trace of such a structure 

 visible, whilst in the two forms under consideration its identity is almost 

 precise. That such a unique structure should have been independently 

 developed in two forms unrelated to each other appears to me to be in 

 the highest degree improbable. 



The main points of divergence from the Phalangers presented by the 

 Wombat are the peculiarities of its dentition, and its extraordinary p.z. S. 1881, 

 caecum (see the description and figure by Prof. Flower, Med. Times and P- 194 - 

 Gazette, Dec. 14, 1872, p. 642). In its teeth being all rootless, as well 

 as in the equality in the number of its incisors, Pliascolomys differs from 

 all other Marsupials. But it is highly probable that this peculiar Bodent- 

 like dentition has been brought about in accordance with its mode of life, 

 and that therefore these features, being adaptive, have in reality less 

 importance in classification than has been assigned to them. Moreover, 

 in a very young Wombat's skull preserved in the Hunterian Museum 

 (1795 D),in which the first three molar teeth only in each jaw have cut 

 the gum and are quite unworn, each lobe of the teeth has two quite 

 distinct, though small cusps ; hence the second and third teeth on each 

 side have four distinct cusps, and the anterior two, as in the Phalangers 

 generally. The caecum is no doubt peculiar, and quite unique amongst 

 Mammalia, any resemblance to the " appendix vermiformis " of the 

 highest Primates being fanciful. If in these points sufficient reason is 

 considered present for elevating the Wombats to the position of a 

 primary group of the Marsupials whether such group be called a tribe 

 or a family is no matter it should not be forgotten that in some features 

 Phascolarctos, too, is nearly as peculiar as Phascolomys itself. These are 

 mainly : the peculiar alisphenoidal bullaof the skull ; the extraordinary 

 complicated liver, with the elongated gall-bladder ; the immensely deve- 



* It would be interesting to investigate the histological structure of this gland, with 

 the object of determining whether or not the resemblance is more than external. 



