238 REMARKS ON POST -TERTIARY PHASCOLOMYID^E, 



adopted as a metrical guide to the recognition of any other 

 Phascolonus bones in the collection, or conversely that any 

 phascolomine bones found to yield the required measurement in 

 two dimensions might, with the consent of other characters, be 

 taken as belonging to the same animal as the skull ; and on this 

 basis the identifications of the proximal end of a second humerus, 

 two femurs, three tibias, a fibula, two scapulas, two ulnas, a radius, 

 ischium, trapezium, trapezoides, astragalus, naviculare, calcaneum 

 and cuboid, or characteristic parts of them, were successively 

 established. It may be well to state distinctly that while these 

 bones are unmistakably phascolomine they almost invariably 

 present conspicuous marks of differentiation from Phascolomys— for 

 examples, the bridge across the entepicondylar canal of the humerus 

 does not subside at once into the shaft as in the pure wombats, 

 recent and extinct, but is continued upwards as an elevated ridge, 

 merging into the deltoid ridge above, and the astragalus has its 

 rotular groove deeply sunken and all its ridges elevated, whereby 

 it is easily discriminated from the smooth-surfaced bone of P. 

 medins and its dwarfed copy in the recent P. platyrhinus. At 

 the same time it must be observed that the extent of differentiation 

 shown by these bones is by no means so great as that which we 

 shall probably find to be correlated with the non-phascolomine 

 incisors of Scepamodon. 



In addition to the above-named bones of the tarsus, there are 

 in the collection several which show that although the animal was 

 as a rule about twice the length of P. platyrhinus, it not unfre- 

 quently exceeded that length by more than one-third. The 

 astragalus referred to is 44 mm. in breadth, against 22 mm. in the 

 living P. platyrhinus, but by its side is a second measuring 51*5, 

 another 55*5, and still another 60 mm., yet no one of these can be 

 specifically distinguished from the rest. The naviculare again is 

 accompanied by two others, the respective lengths of the three 

 being 41*5, 54, and 56. With the largest astragalus are associated 

 its naviculare, calcaneum, and cuboid, and arranged with them are 

 the four metatarsals, but these have been contributed by other 

 feet. Of foot bones of this larger size there are in all sixteen 



