457 



advance of the hind end. The fore-and-aft extent of the crown of this tooth, as in that 

 of the upper jaw, is less than that of the next tooth (d 4). 



In all these modifications the analogies of the before-described genera and species of 

 extinct Macropodidce, support the conclusion that we have in the subjects of Plate XCI. 

 the requisite completion of our knowledge of the dental characters of the chief subjects 

 of Plate XC, viz. of the new and interesting genus and species Procoptodon Pusio. 



I have next to submit, as in the case of Sthenurus, evidences of a larger species of 

 the genus. 



§ 23. Procoptodon Bapha, Ow. — The size of the premolar (Plate XC. fig. 8,^3) in 

 the fragment of lower jaw of the immature Procoptodon there figured, indicates it to 

 have come from another and larger species than Procoptodon Pusio, yet of inferior size 

 to Procopt. Goliah (Plate XCV. fig. 7, p 3) ; the shape of the incisor indicates likewise 

 a difference of species. 



The size of the remains of the two anterior fully developed molars (Plate XC. 

 fig. 8, d 2, d 3), in proportion to the jaw supporting them, suggested immaturity, and the 

 excavation of the bone beneath them exposed the crown and beginning of the fangs of 

 a large and thick premolar, of the crushing type of the present genus. 



The outer part of the crown (ib. fig. 8, p 3) is divided into two subequal lobes by a 

 marginal notch, from the apex of which a linear groove is continued down the outer side 

 of the crown. The height of this is 6 lines, the fore-and-aft extent is 7 lines ; the breadth 

 behind is 5 lines. The crown bulges out above the roots, the hinder one of which 

 bifurcates 6 lines below the crown. The enamel is smooth, white, and the exposed parts 

 show more or less convexity. 



The base of the broken crown of the first deciduous molar (ib. fig. 11, d 2) is triangular, 

 with the angles rounded off and the base turned backward ; the length of the triangle is 

 4 lines, the basal breadth 3 lines. The base of the next bilophodont tooth (d 3) is sub- 

 quadrate, 5^ lines in length, 5 lines in breadth. 



The diastemal tract (figs. 8, 9, & 11, I, si) has a characteristic shortness; it is con- 

 tinued with, at first, a feeble concavity almost straight on to the outlet of the incisive 

 alveolus, to which it slightly bends down. The outlet of the dental canal (fig. 8, v), 

 about 2 lines below the diastemal border, would be about 7 lines from the alveolar 

 outlet were this entire. The lower or symphysial border (figs. 8, 9, s, s") rises to the 

 alveolar outlet at a less open angle with the lower border of the horizontal ramus 

 than in Sthenurus*. The syndesmotic articular surface is flat, rough, and is continued, 

 well defined, to the outlet; it indicates the generic firmer union of the rami than in 

 the type Kangaroos, and a greater development of the uniting or binding structure than 

 in Sthenurus^. 



The thickness of the ramus at the formative cell of the premolar, in Procoptodon 

 Bapha, is 10^ lines (Plate XC. fig. 10). The base of the incisor (ib. figs. 8 & 9, i) 

 indicates a tooth of less relative thickness than in Procoptodon Goliah. The fractured 

 * Plate LXXXII. fig. 6. + Ib. ib. s. 



