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Show 814 DR. J. MURIE ON PHASCOLOMYS PLATYRHINUS. [June 27, most like each other in form and size -. in two specimens the first measured 5-^ inches in its long diameter, the second 6"; but in P. platyrhinus it is considerably the stronger and thicker, the shaft being somewhat compressed from before backwards, whereas it is nearly round in wombat. The length of the femur in P. latifrons is 5 ^ inches, but, although shorter than in P. wombat, it is much stouter; the shaft is also straighter. The prominent antero-posteriorly compressed outer ridge, which extends downwards from the great trochanter, so as to form a kind of third trochanter in P. wombat and P. platyrhinus, is absent in P. latifrons ; a roughening behind the shaft merely represents this. Tibia and Fibula.-P. platyrhinus and P. wombat again approximate in the form of the tibia; it is much the broader antero-posteriorly in the former, while the shaft is straighter in the latter. The shaft of P. latifrons is still more laterally compressed; and about the centre of the shaft the anterior edge is slightly bent outwards, which also takes place in a less degree in P. platyrhinus, but not in P. wombat. The lengths of these bones are respectively 4"*7, 4"*5, and 4"*4. The articulating surfaces in P. latifrons are abruptly flattened and spread out, but they are more sloping in the other species. The tibia seems to be reversed, and differs in length, being -^ of an inch shorter in P. latifrons ; and the shaft is rather more compressed laterally ; at least it is broader and stronger antero-posteriorly, the strong sharp ridge continued in front, the head rising to be a roughened protuberance in the upper part of the middle one-third of the shaft, as Owen has described in the Koala*. The fibula is of about equal length in P. wombat and P. latifrons, but the shaft is straighter and stouter in P. latifrons; the interosseous space is also wider in it, giving a greater breadth for the origin of the anterior muscles of the leg. Metatarsal and Phalangeal Bones.-In the hind foot P. platyrhinus and P. wombat agree in having the index digit somewhat shorter than the third, and in having its proximal phalanx decidedly shorter than the metatarsal; whereas in P. latifrons the index is the longest, and has its proximal phalanx and metatarsal of almost equal length. This circumstance gives the hind foot of P. latifrons quite a characteristic shape. Conclusion. In reviewing the observations contained in tbe present paper it is necessary to take into account the results of m y former communication on the Hairy-nosed Wombat and the species of Phascolomys generally. What the axial and appendicular skeletons further show is, that P. wombat and P. platyrhinus are closely related in several particulars, and that P. latifrons differs decidedly from them both. Phascolomys platyrhinus, it would seem, can only be recognized as specifically distinct from P. wombat in a zoological sense. Size and colour, which last varies considerably, point out a departure from the type of P. wombat. * Trans. Zool. Soc. vol. ii. p. 405. |
