484 



Macropus. The surface, worn by attrition of the upper incisorB, is a broad angular 

 notch, whence I infer that it has been made chiefly, if not exclusively, by the vertically 

 directed crown of a disproportionately developed anterior upper incisor. 



A small portion (d 1 , fig. 2) of the lower inflected border of the mandible is preserved ; 

 but the longitudinal channel (b) which it bounded is traceable above the line of fracture. 

 The thinness of this part of the lower border of the ramus makes it liable to be broken 

 away in the fossil. 



The extent of the true or " marsupially " inflected angle (a) is well defined, although 

 it also has suffered fracture. The longitudinal extent of the angular fracture is 

 1 inch ; but it is continued along the ridge or plate extending upward to form the 

 hinder inflected border of the ascending ramus, which border is also broken away. 

 The smooth channel, between a and d ! , fig. 2, dividing the inflected part of the lower 

 border of the horizontal ramus from the inflected angle, repeats that in Nototherium, 

 shown in Plate XLI. fig. 2, between d' and ae; but it is relatively less or narrower in 

 Procoptodon. It is not present in Macropus or Phascolomys. 



The inner (mesial) surface of the ascending ramus (fig. 2) is divided into two depres- 

 sions by a ridge continued from the postal veolar angle (fig. 2, t) upward and backward 

 to the subcondylar protuberance, answering to that in Nototherium, marked n in 

 Plate XLI. fig. 2. The ridge (r, fig. 2, Plate CXXVIII.) is not present in Nototherium 

 and is faint in Phascolomys (comp. Plate LV. fig. 3, t). It is very short where it is 

 recognizable in Macropus (Plate LXXXIV. fig. 12); and in Procoptodon it subsides 

 ere it reaches the subcondylar protuberance (n). The depression anterior to the ridge 

 (r, fig. 2) is divided into the " ectalveolar groove" (u) and the ecto-crotaphyte surface (o). 

 The deeper depression (e, e 1 ) posterior to the ridge (r) is perforated by the " fenestra! 

 foramen " (f). This foramen is above the level of the grinders in Procoptodon, but is 

 below that level in Macropus. It is not present in Nototherium, and is very small and 

 low-placed when it exists in Phascolomys. In Procoptodon Rapha it is of a full oval 

 form, 6 lines in long diameter; it opens into the upper part of the large and deep 

 - fenestral vacuity " (fig. 3, c), at the bottom of which begins the dental canal. 



In the chief characters in which Procoptodon deviates from the type Macropodida 1 

 (Macropus, e. g.), it approaches Phascolomys, but more closely Nototherium. 



The halves of the lower jaw have lost all reciprocal movement at the symphysis; and 

 where bony confluence has not begun, the greater superficial extent and deep sutural 

 interlocking surface of the apposed parts of the rami bind them firmly together. The 

 inflected border (dl) anterior to the true " angle " (a) in Procoptodon is a significant 

 mark of affinity to Nototherium, and concurs with the type of the grinders in demon- 

 strating this relation. 



On making first acquaintance with Procoptodon Rapha, a misgiving question suggested 

 itself, viz. whether its inferiority of size to Proc. Goliah might not indicate a sexual 

 character belonging to the female of that species. But such inferiority, which is 

 manifested in the females of most existing Kangaroos, is shown in general size and 



