190 ON BRACHALLETES PALMERI AN EXTINCT MARSUPIAL, 



may be noted that the depression bounding that side of the 

 column supporting the part of the head above is filled up, but on 

 the other hand that a ridge runs down the hind edge of the inner 

 side of the shaft from near the brim of the cavity for the inner 

 condyle. On the whole the bone gives the impression of a better 

 knit, and more muscular animal, of a size too superior, to be 

 included in the same species with S. ursinus — one whose las^ 

 molar must have equalled, or nearly equalled in size, the great 

 sectorial of a large dog and must have been fully competent to 

 the work whereof so many traces have been left. 



On Brachalletes Palmeri an Extinct Marsupial. 

 By Charles W. De Yis, B.A. 



A conspicuous feature in the skeletons of kangaroos is the 

 inordinate elevation of the great trochanter of the femur. In the 

 level of its apex above that of the * head ' of the bone there is an 

 excess pervading the family, neither individual, specific, nor generic 

 variation being carried to any great extent. The fact will appear 

 more precisely evident if we measure the gluteal angle in several 

 of the genera — and by gluteal angle is meant the angle made 

 with the long axis of the bone by a straight line touching the top 

 of the trochanter and the summit of the head. In Macropus 

 major we find it to be 52° in M. rufus, 54° in Halmaturus dor sails, 

 56° in the femur figured in the Foss. Mamm. of Aust. as that of 

 Palorchestes Azael, it is 46 Q and in six other fossil species examined 

 for the purpose it ranges from 60° to 45°. The value of this 

 angle is the measure of the leaping ability of the animal, the 

 propellers of the weighty trunk acting on the limb to be extended 

 with a force proportionate, inversely to the inclination, and 

 directly to the resultant length of the line of leverage. Whence 

 we may conclude that any considerable depression of the tro- 

 chanter is an index to concomitant modifications of the general 

 economy sufficient to bring about at least very distinct generic 

 differentiation. In this predicament stands a femur lately found 



