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Show 1881.] MR. W. A. FORBES ON THE KOALA. 193 limbs are equal, the tibia and fibula are widely separated, excepting, of course, at the extremities; and the stomach is simple', as in the Phalanger group. On the other hand, we perceive in the Koala an animal possessing all the essential characters of Phalangista, but in which the stomach is provided with a peculiar glandular apparatus, and the tail is wanting, as in the Wombat. The two animals agree, moreover, very closely in the structure of the humerus ; they agree in the non-possession of a patella, in the absence of a Ugamentum teres2, and in the outermost of the articular surfaces of the upper extremity of the tibia being continuous with the articular surface of the fibula. The skull of the Koala, as compared with that of a typical Phalangista, differs in having the posterior palatine openings confined to the palatine bone, which is also the case in the W o m b a t ; the lower jaw differs in the greater extent of the symphysis menti; and, lastly, an approximation to that Rodent-like type of dentition which is exhibited by the W o m b a t is perceptible in the Koala, in the smaller development of the posterior incisors and canines of the upper jaw, and the total absence of any of those premolars which, in the typical Phalangers, intervene between the 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 M r. 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 additional superficial sulci, and, finally, in the structure of the female reproductive 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 m y mind, the most convincing token of their affinity is their possession of the peculiar gastric gland3 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 m e to be in the highest degree improbable. The main points of divergence from the Phalangers presented by the W o m b a t are the peculiarities of its dentition, and its extra- 1 I suppose by this is meant as opposed to the sacculated stomach of the Kangaroos. 2 As regards these last two characters, it must be observed that the first is a character practically common to all Marsupials, excepting the Peramelidte (of. Flower, ' Osteology of Mammalia,' 2nd ed. p. 306). As regards the alleged absence of a ligamentum teres, I find it perfectly well developed in fresh specimens of both Koala and W o m b a t ; on the femur the depression for it, though not distinct, is traceable. 3 It woidd be interesting to investigate the histological structure of this gland, with the object of determining whether or not the resemblance is more an external. PROC. ZOOL. Soc-1881, No. XIII, 13 |