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



some of the parts, due, no doubt, to age. The clitoris, however, is 

 free at the apex and slightly bilobed'. 



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

 accompanying figures (figs. 3-6), 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 quadrigemina largely 

 exposed behind ; and in consequence the cerebellum is left entirely 

 uncovered : indeed, when 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 07 inch. Viewed from the side, their superior contour 

 is seen to be but little arched behind, whilst anteriorly it slopes down- 

 wards away rather suddenly towards the olfactory lobes. These last 

 are not large, and but Httle" exposed ; in fact, in the undisturbed state, 

 they are covered, when viewed from above, by the hemispheres. 

 The temporal lobe is small. Superiorly the hemispheres, save for 

 a few slight vascular impressions, are altogether smooth ; laterally, 

 a well-defined sulcus, running from the temporal lobe forwards, and 

 curved, first upwards and then downwards, is visible. Anteriorly, 

 this separates off the olfactory tract from the side walls of the hemi- 

 spheres. A slight indentation, about halfway along its course, at 

 the top of its upward convexity, may represent a rudimentary 

 Sylvian fissure. Just behind this is a second similar, though smaller, 

 impression. The olfactory ganglion is large, as is the tract. 

 Internally, the characteristic features of the Marsupial brain - are 

 distinct, the corpus callosum being small and indistinct, and the ante- 

 rior commissure very large. The hippocampal sulcus is distinct and 



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

 differences of importance whatever from the type here des Tibed. The Fallopian 

 tubes are apparently longer, and their fimbriated extremities better developed. 

 The form of the ovaries, and the disposition of the uteri, vaginse, and urino- 

 genital sinus seem to be nearly precisely similar in the two genera. 



In Phalangista vuJfina, on the other hand, considerable differences occur. 

 The Fallopian tubes are shorter in proportion to the uteri, and are more con-fO- 

 luted. The uteri are more distinct from the Fallopian tubes, are more capa- 

 cious, and strongly curved outwards. Each os tincm projects as a prominent 

 and quite fi-ee papilla into a common vaginal chamber, formed by the coalescence 

 and fusion of the two divcriicida present in Phascolomys and Phascolarctos. 

 This chamber is capacious, and has only a very slight indication of a median 

 septum left. 



In Belideus scwretis the Fallopian tubes and uteri resemble those of Phalan- 

 gista. The vaginte, 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 

 Petaunis {=£eNdeus?), according to Owen (Anat. Vert. iii. p. 682), where 

 the vaginse are also long and curved, the culs-de-sac remain separate. 



-■" Vide Flower, Phil. Trans. 1865, p. 647. 



