422 



ualabatus (Plate LXXXIV. figs. 10, 12) agrees with Macropus and differs from 

 St he ii urns. 



The lower border of the crown of the incisor, with the free end of that tooth, is 

 broken away in the Oxford specimen, but enough of the crown remains to show that it 

 is shorter but vertically broader than in Macropus proper. The enamel is confined 

 to the under and outer sides ; the radical cement encroaches on the outer enamel in an 

 angular form (Plate LXXXII. fig. 5, i). The upper border of the base of the crown is 

 trenchant ; the tooth gradually gains in thickness to the lower border, but even here it 

 is less than half the vertical breadth of the crown ; the inner surface, behind the 

 working one, is vertically more concave than in Macropus Titan. The hind part of the 

 narrow surface of attrition upon the upper edge of the crown begins half an inch from 

 the hind border of the enamel. 



The premolar with a fore-and-aft extent of crown of 8 lines (17 millims.), a vertical 

 extent of 6 lines (12 millims.), and a greatest breadth, near the hind border, of 3 

 lines (6^ millims.), is, externally (ib. fig. 5, p b), divided into two subequal lobes ; 

 but the vertical fissure runs obliquely backward and inward, so that the lobe 

 forming the anterior half of the outer surface of the crown forms the whole of the 

 inner surface. 



This lobe has a slight prebasal prominence, and is divided above by two vertical 

 transverse fissures, the foremost of which is in view on the outer surface, extending 

 nearly halfway down the crown ; this fissure widens to the upper border, where the two 

 divisions of the lobe which it separates are linked by a slender longitudinal bar of 

 enamel. The second transverse fissure is not so widened above, but the rudiment of an 

 enamel link appears behind the second transverse division of this lobe ; the third 

 division is less definitely cleft or marked off from the rest of the antero-internal lobe, 

 which is continued with a trenchant border to the back part of the crown to which it 

 descends ; vertical depressions, hardly to be called fissures, are indicated on the inner 

 surface of this hinder portion of the lobe (Plate LXXXII. fig. 6, p a). The postero- 

 external lobe (ib. fig. 5, p z) has a simple trenchant edge, describing a slight convexity 

 lengthwise ; it is connected with the postinternal lobe by two transverse enamel links, 

 the foremost being the largest (ib. fig. 8, p s). 



The outer surface of this complex tooth (p s) is shown in fig. 5, the inner surface in 

 fig. 6, and the upper surface in fig. 8. The homologous tooth in Ilalmaturus ualabatus 

 (Plate LXXXIV. figs. 10, 11, 12, p z) shows nothing of the complexity answerable to 

 that which renders the upper premolar of that Wallaby so similar to the upper premolar 

 of 8th minis ; it has an undivided trenchant crown, slightly thickened behind, with some 

 very feeble indications of vertical grooving on both inner and outer sides. Two teeth 

 (d 2, d 3) have been displaced by the rise of p 3 in the Oxford specimen of Sthenurus 

 Atlas ( Plate LXXXII. figs. 5-8) : one of these, viz. d 3, is retained in the type specimen 

 ^ib. figs. 3 & 4, d 3). 



The molar following^ a in Plate LXXXII. figs. 5, 6, 8, answers to d i in the placental 



