194 MR. W. A. FORBES ON THE KOALA. [Jan. 18, 



ordinary csecum (see tlie description and figure by Prof. Flower, 

 Med. Times and Gazette, Dec. 14, 1872, p. (342). In its teeth being 

 all rootless, as well as in the equality in the number of its incisors, 

 Phascolomys differs from all other Marsupials. But it is highly 

 probable that this peculiar Rodent-like dentition has been brought 

 about in accordance vvith its mode of life, and that therefore these 

 features, being adaptive, have in reality less importance in classifi- 

 cation than has been assigned to them. Moreover, in a very young 

 Wombat's skull preserved in the Hunterian Museum (1/95 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 cusjjs ; 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 vermi- 

 formis" of the highest Primates being fanciful. If in these points 

 suflHcient 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 P/iascolarctos, too, is nearly as pecu- 

 liar as Phascolomys itself, /fhese are mainly : — the peculiar alisphe- 

 uoidal bulla of the skull ; the extraordinary complicated liver, with 

 the elongated gall-bladder ; the immensely developed caecum and 

 caecum^like ascending colon, with their longitudinal folds of mucous 

 membrane ; and the absence of an azygos lobe to the lungs, the 

 Wombats agreeing with the Phalangers in possessing one. Hence it 

 appears to me to be a more natural course to keep these three groups 

 together as subdivisions of a larger one, though whether that one be 

 called a family, or made into a larger section, will depend on the value 

 attached to those ideas by different naturalists. Adopting the former 

 as most convenient, they might be defined briefly as follows : — 



Phalangistid^. 



Diprotodout Marsupialia, with clavicles, and not more than six 

 incisors above. The hallux present ; the 2nd and 3rd digits of the pes 

 smaller than the others, and more or less united together by integu- 

 ment. Stomach not sacculated. Caecum present. Glans penis 

 more or less bilobed ; vaginae provided with median culs-de-sac which 

 may unite. 



I. Phalangistin^. 



Teeth rooted; superior" incisors 3.3; at least one small addi- 

 tional premolar on each side above. Tail well developed. No 

 cheek-pouches. Stomach and ascending colon simple. Caecum 

 long, simple. Liver not complicated by secondary sulci, and with 

 distinct caudate and Spigelian lobes. Lungs with an azygos lobe. 

 Vaginal culs-de-sac coalesced (at least in PhalaTigista). 



Phalangista, Cuscus, BeUdeus\ Acrobata\ Vromicia\ 



1 For au oijportunity of dissecting examples ol' these genera I am indebted to 

 the liberality of our President. 



