];V II. It. SCOTT A.M> CLIVE E. LORD. 99 



facet. In X. tasmanicum, the astragalus overhangs the 

 caloaneum, owing to the greater slope (noted supra), thus 

 masking completely the primitive character of a fibular 

 calcaneal articulation, strongly manifested by X. mitchelli. 

 To followers of the evolutionary trend, this character will 

 serve to recall the fact that the most primitive member 

 of the sub-order Perissodactyla, namely, Macrauchenia, ex- 

 hibited this character, as also did the several meml 

 the sub-order Taxodontia. The suppression of such an 

 osteologieal item should be 01 lie importanci 



In conformation with the abovenamed difference 

 the two astragali under consideration, ev rv other articular 

 surface, and facette, shows similar variations, the details 

 of which it is unnecessary to give, since the articul 

 of the fibula with the calcaneum, by a well-marked sur- 

 face, will serve bo classify the moiety with the 

 Megacerathint Nototheria, and nee of smh will 



relegate it to the Leptocerathiru group. 



The total height of the superimposed bones in -V. 

 tasmanicum is 120 mm., and that of X. mitchelli 122 mm.. 

 t'n ir astragalar widths (in articular position) being 82 

 mm. and 1A mm. respect r. cation of 



of calcanei th best guide in tie absence of the 

 evid me yielded by tie fibular facet, i- thai of the whole 

 articular surface. In .V. mitchelli, t ; are 80 mm. in 



antero-posterior length, with a width of 70 mm., whih in 

 .V. tasmanicum, the surface is 60 mm. s 60 mm. The. 

 r >lope in X. mitchelli is only •"■' 

 in X. tasmanicum it i* 50 d When perfect, 



the t v. !' i n fairly similar in point 



of size and robusl ness. I ur that t he 



bones of the t arsus and toes are unknown in X . tasinan 

 as the iction may have- — indeed, w< 



vinced rausl have — shown grades when com- 



pared with those of X. mitcht 



As far as we can judge (working only from ph< 

 graphs of the foot of h ticular cup for the 



• is form d in th Not ■>' - im, in about th 

 proportions as that which obtains in Diprotodon, namely — 



(1) The lar. vicular. 



Th d x.i in importaj _ that contributed by 



tun. 



(3) Th.- minimum shave being supplied by the cuboid. 



'l.i In the kangaroo, tli* pnnative character is retaine-1, in Mo, 

 the fib articular : the cal- 

 caneum— to ■.;. that the astragalus at 1>< tip. in 

 i I »n in V. m 'clielli, and its total sup- 

 pression in V. ' to be kept in si^ht. 



