110 FOSSIL JAWS OF MACROPODID.E, 



vary from 28-3 to 29'1 (3); the first two are 19-5 (1); the pre- 

 molar measures from lO'O to 13*0 (8). The true molar series 

 ranges from 40-0 to 48-1 (8); the last three from 34-3 to 41 -1 (9); 

 the last two from 23-8 to 28-6 (12); the first three from 29-4 to 

 38-1 (5); the first two from 20-5 to 22-6 (4); m.-, m/^ are 27*1 

 (1); m.3 13-0 (1); m.-* is from 13-2 to 14-4(7). The width of 

 m.'^ is from 8*0 to 10-5 (37). The anterior depth of the mandible 

 varies from 22-0 to 30'0 (20); the posterior from 19-4 to 29-9 (21); 

 the thickness from 12-7 to 18-8 (31). 



It will be apparent from these measurements that though tlieir 

 maxima overlap in some cases the minima of H. anak the 

 differences between their minima and the maxima of the other 

 are far too great to be ascribed to the elasticity of a single species 

 even were all the teeth indistinguishable. The existence of a 

 dwarfed variety of H. anak conterminous and contemporaneous 

 with it is too unlikely U) h<d worth considering. 



The probability that upjier and lower jaws are in this case 

 rightly associated rests on the grounds of corresponding size and 

 premolar structure. 



Form. 



Mandibular.- — The premolar p.^ (PI. xvii. fig. 12) as extracted 

 from its chamber in an advanced stage of growth is an elongate- 

 ovate symmetrical tooth with a cuneiform crown and diameters 

 10-7 : 4-4. The crown is compressed as to its mesial two-thirds, 

 more deeply on the inner side. Three mesial ribs on each side 

 form serrations on - the crest which is central. There is no 

 dilatation or tumidity of the intero-posterior angle, but the end of 

 the crest inclines slightly inwards. In the w^orn state these teeth 

 can be distinguished from old teeth of //. anak only by their size. 



The deciduous j^remolar p. "^ (PL xvii. fig. 11) is very similar to 

 that of //. anak, convex on the outer, nearly straight on the inner 

 side, with a slightly developed intero-posterior cus23 which renders 

 the inner side somewhat concave posteriorly. Diameters 7*0 x 

 3-9. 



Maxilhry.- — The premolar p."* (PI. xvii. fig. 13) is elongate- 

 triangular, with diameters 13 x 7*8 (basal). Crest central 



