455 



fig. 7 with 4 will do of greater depth, relatively to the size of the teeth, in the species 

 in which those teeth have a more complex grinding-surface. The characters of this 

 complexity, especially in connexion with the mid link, and the conformity of antero- 

 posterior extent of the mandibular molars (m i, m 2, fig. 9) with the homotypal maxillary 

 teeth of Procoptodon Pusio (Plate XC. fig. 6), led me to suspect that they might be parts 

 of the same species — a suspicion which the subsequent reception of the greater propor- 

 tion of the lower jaw and teeth, figured in Plate XCL, has confirmed. 



For this evidence of the mandible and its dentition of Procoptodon Pusio I am indebted 

 to George B. King, Esq., of Gowrie Station, Queensland. It was discovered in the bed 

 of a tributary of the Condamine River, called " King's Creek." It consists of the right 

 ramus, part of the left, with the uniting symphysis, fractured anteriorly, where the 

 implanted roots of the two incisors are shown (fig. 4, i, i). In the right ramus are pre- 

 served the last molar [m 3), part of the second (m 2), and the bases and roots of the three 

 antecedent grinders (m 1, d 4, p 3). The detached portion of the left ramus (figs. 2 & 3) 

 and part of a right ramus of another mandible (fig. 5) afford the illustrations of the 

 dentition, figured, as restored, in fig. 1. 



As compared with the typical Kangaroos the diastema is short ; the symphysis, in 

 like manner, is short and thick, and its anterior surface (s, fig. 2) is directed upward and 

 forward at an obtuse angle with the axis of the ramus, not extended, as in Macroipus 

 proper, in a direction with that axis. The incisors accordingly are much less pro- 

 cumbent, but yet slope forward from the perpendicular. Their direction I estimate 

 from that of the roots remaining in the symphysial part of the rami. 



The section of the incisor made by the fracture (fig. 4, i) is elliptic, the long axis 

 inclined a little outward from the vertical line, 6 lines by 4 lines. The interspace of 

 bony structure at the place of fracture would not be that of the exposed crowns ; the 

 incisors converge as they advance. The middle of the outer surface of the symphysis is 

 slightly produced, giving a convex curve to that part of the slope ; above which the 

 contour becomes rather concave through a production of the floor of the incisor's socket 

 (fig. 2, s). The breadth of the symphysis external to the broken part of the sockets is 

 1 inch ; at the fore part of those of the premolar it is 2 inches ; the breadth of the 

 mandible at the hind end of the symphysis is 2 inches 10 lines; the length of the pre- 

 served part of the symphysis is 2 inches 6 lines, and I estimate as much, at least, to have 

 been broken away. On the inner or posterior surface of the symphysis is a large and 

 deep depression (fig. I, s), just opposite the prominence on the outer or anterior surface. 

 The vertical extent of the ramus at the hind end of the symphysis is 1 inch 10 lines ; it 

 slightly decreases as the ramus recedes. A shallow channel below both the outer and 

 inner alveolar border gives this the appearance of a low ridge ; below the outer channel 

 the surface swells out into a bold convexity ; the inner vertical surface deviates from 

 flatness by being feebly convex. Longitudinally it is rather more convex. Behind the 

 last molar the inner surface begins to be divided into two shallow concavities (fig. 3, b, c) 

 by the inward production of the part of the jaw which would have been continued into 



