OiV THE ANATOMY OF THE KOALA. 183 



cloaca so formed is surrounded by a common fold of muscles and integu- 

 ment. A small, flattened, linguiform clitoris, not free at its apex, with 

 two grooves above and about 0'2 inch long, is developed on the anterior 

 Avail of the cloaca, beginning at the level where the rectum and urino- 

 genital canal meet. 



A second specimen examined an adult female that has been preserved 

 in spirit, and which, judging from the condition of its mammae, has been 

 a mother shows exactly the same relations of these parts as that here 

 described, the only differences being in the sizes of some of the parts, P. Z. S. J881, 

 due, no doubt, to age. The clitoris, however, is free at the apex and p< ' 

 slightly bilobed *. 



The brain of the Koala is represented of the natural size in the 

 accompanying figures (figs. 3-6, p. 185), of which that representing its 

 superior aspect was taken from the brain before being removed from the 

 cranial cavity, and therefore unaltered by displacement or hardening in 

 spirit. The other three figures are drawn from the brain after hardening 

 in alcohol for some months. 



The cerebral hemispheres are remarkable for their simple surface, 

 which is broken up by no convolutions. Broadest behind, they taper 

 forwardly, and so are somewhat pyriform in outline when viewed from 

 above. They leave the corpora quadriyemina largely exposed behind ; 

 and in consequence the cerebellum is left entirely uncovered : indeed, 

 w^hen the parts are undisturbed (fig. 3) it is not even in contact with 

 the cerebral hemispheres. The greatest length of the cerebral hemispheres 

 is about 1'2 inch ; their greatest depth about 0*7 inch. Viewed from the 

 side, their superior contour is seen to be but little arched behind, whilst 

 anteriorly it slopes downwards away rather suddenly towards the olfactory 



* In Phascolomys wombat, in a two-thirds grown female, I can detect no differences 

 of importance whatever from the type here described. The Fallopian tubes are 

 apparently longer, and their fimbriated extremities better developed. The form of the 

 ovaries, and the disposition of the uteri, vaginae, and urino-genital sinus seem to be 

 nearly precisely similar in the two genera. 



In Phalangista vulpina, on the other hand, considerable differences occur. The 

 Fallopian tubes are shorter in proportion to the uteri, and are more convoluted. The 

 uteri are more distinct from the Fallopian tubes, are more capacious, and strongly 

 curved outwards. Each os tincce projects as a prominent and quite free papilla into a 

 common vaginal chamber, formed by the coalescence and fusion of the two diverticula 

 present in Phascolomys and Phascolarctos. This chamber is capacious, and has only a 

 very slight indication of a median septum left. 



In Belideus sciureus the Fallopian tubes and uteri resemble those of Phalavgista. 

 The vaginae, however, are much longer and curved on themselves, much as in the 

 Kangaroos. There are apparently two small culs-de-sac ; but the specimen examined 

 does not allow me to say whether or no they unite. In Petaurus ( = Belideus ?), accord- 

 ing to Owen (Anat. Vert. iii. p. 682), where the vagina 1 are also long and curved, the 

 culs-de-sac remain separate. 



