380 



The four retained molars on the left side of the upper jaw present the two chief 

 transverse ridges as in the lower jaw ; but they are broader in proportion to their length 

 than in that jaw, and the curve of the ridges (as shown in m a, fig. 3) where they are 

 least worn is slightly concave backward, instead of forward as in the lower jaw 

 (fig. G : in this figure the grinding-surface of d 4, pushed out of line in the lower 

 jaw, is added in front of the figure of the tooth so displaced). 



The first, perhaps chief, difference between Macropus rufus, Dsm., and M. major, 

 Shaw (PI. LXXX. fig. 17), is the smaller relative extent of the crown of the upper and 

 outer incisor, i 3, which shows only one shallow vertical impression along the middle of 

 the outer surface (PI. LXV1. fig. 1). On this mainly would rest its claim to a sub- 

 generic distinction, such as Gould has indicated by the term Osphranter; but the 

 incisor-character is not repeated in other species of Osphranter (M. robustus, M. anti- 

 lopinus, e. g.). The above dental distinction of M. rufus, however, is associated with 

 several cranial ones. In the skull of a full-sized male, with teeth more worn than in 

 that of a M. major compared with it, the temporal ridges have not met along the 

 sagittal suture, but are separated by a tract half an inch in breadth, along the middle 

 of which the sagittal suture persists. The anterior angles of the parietals give better 

 indications of postorbital tubercles. These, however, are not more shown in M. rufus 

 than in M. major. In a skull of the M. [Osphranter) robustus compared, which retains 

 the premolar (^ 3) with four fully developed molars behind, the sagittal crest is better 

 marked than in M. major and M. rufus, in which that premolar is shed. 



The Great Red Kangaroo is one of the largest of the tribe ; yet the skull indicates 

 a less powerful animal. The paroccipitals are more slender. The zygomatic arches 

 have less span and depth ; the masseteric process is much shorter ; the ridge above the 

 fore part of its base is due to the malar more than to the maxillary. The mandible is 

 more slender ; the coronoid process is shorter and narrower from before backward ; the 

 depth of the ramus behind the molar series is notably less in M. rufus ; yet the last 

 molar, with the same fore-and-aft extent as in M. major, is broader. 



The basioccipital ridge in M. rufus is sharper. The upper border of the foramen 

 magnum is notched. The condyles are narrower, and the ectocondylar grooves deeper 

 and wider. The superoccipital is less elevated and more truncate atop ; the base of 

 the occiput is narrower. The facial plate of the lacrymal is broader, and the lower 

 and larger foramen is more external. The antorbital foramen is further from the 

 orbit. The premolar part of the skull is shorter and deeper ; the maxillary out- 

 swelling is less definite. The facial plate of the premaxillary is broader antero- 

 posterior^. The incisive foramina are longer and further from the third incisors. 

 The postpalatal apertures are larger, especially the right one ; but this may be a 

 variety : the bony palate behind them shows more and larger irregular perforations, 

 the hamular process of the pterygoid is less defined, than in Macropus major. 



Such are the chief differences observable in the skulls of M. rufus and M. major ; 



