418 



its inner side and very little posterior to it, the intervening bony plate with a sharp 

 concave edge forming the inner border of the entorbital foramen and the antero- 

 external border of the more oblique spheno-palatine foramen. 



In Sthenurus Atlas the upper border of the entorbital fossa, in its shortness and 

 degree of sharpness, is more like that in Macropus Titan. The inner wall of the orbit 

 ascends rather more directly therefrom than in Macropus major. The pterygo-palatine 

 foramen in the palatine part of the inner orbital wall is more minute in Osphranter 

 than in Macropus. In Phascolagus erubescens the proximity of the first and second 

 foramina is closer than in Osphranter. 



In the unique skull of Boriogale magnus it appears that part of the inner wall of the 

 orbit completing, above, the circumference of the second foramen is unossified ; and 

 such part of the skull in a petrified state would show only one large circular orifice, 

 answering to the first or entorbital one in Macropus major and Macropus Titan. In 

 the comparison of the orbital part of the skull, Macropus Titan, in the relative size and 

 position of the two anterior foramina (entorbital and spheno-palatine), agrees with 

 Macropus major more closely than with the above-cited representatives of other sub- 

 genera of living Kangaroos. 



From the upper and anterior margin of the entorbital foramen (Plate LXXXIV. fig. 5, o) 

 rises a plate of bone (n, figs. 4 & 5), quickly narrowing to form part of the inner wall of 

 the orbit, or partition-wall between that cavity and the nasal one. This structure implies a 

 less relative depth, or diameter, of the orbit from without inward or transversely than in 

 the existing genera above cited*. But a nearer approach to the above-defined orbital 

 character in Phascolagus and Sthenurus appears in Boriogale, where the nerves and vessels, 

 passing by the floor of the orbit to the maxilla, leave only one mark of perforation of that 

 floor by a subcircular entry to the canal, the other elements forming the second and con- 

 tiguous foramen in Macropus, &c, here traversing the above-surmised membranous 

 or unossified state of the inner and under wall of the orbit. The reduced ossified part 

 continued from above the bony canal rises somewhat like the lamellate process shown 

 at n, figs. 4 & 5, in Sthenurus. Boriogale also shows the longitudinal depression above 

 and exterior to the entorbital foramen, terminating anteriorly in a blind end, as is seen 

 in Sthenurus and in a feebler degree in Halmaturus. 



The outlet of the suborbital canal in Sthenurus Atlas is relatively further from the 

 orbit than in Macropus major, in which respect the present fossil resembles Osphranter 

 and Halmaturus: the distance in the present example of Sthenurus Atlas is 1 inch 1 line. 

 The lower part only of the outlet and canal is preserved in the present specimen ; and 

 below the outlet is a second small foramen, the canal from which passes backward, not 

 downward as in Macropus Titan. 



There is not sufficient of the bony palate preserved to determine whether it was as 

 entire as in the larger living Kangaroos (Macropus major, Osphranter robustus, Phasco- 



* Whence may be inferred a smaller eyeball, associated perhaps with more diurnal habits, than in the still 

 living Kangaroos. 



