417 



to the base of the crown, whilst the oblique extension of that fissure inward and backward 

 gave a transversely subbilobed character to the unworn surface of the hinder part of 

 the tooth. As, however, I have since obtained a portion of the upper jaw with the right 

 series of molars of the same species, I will proceed with its description before entering 

 upon further and requisite details of the mandibular evidences originally indicating the 

 present extinct subgenus of Kangaroo. 



The instructive illustration of the maxillary dentition of Sthenurus Atlas (Plate 

 LXXX1V. figs. 4, 5, 6) formed part of a collection of fossils sent to me by F. G. Water- 

 house, Esq., Cor.M.Z.S., Curator of the Museum of Natural History in Adelaide, South 

 Australia, in the freshwater deposits of which province this fossil was obtained. 



The portion of maxilla includes the masseteric process (ib. fig. 4, 21), the hind border 

 of the maxillary pier from which it is continued being parallel to the interval between 

 the penultimate (m 2) and last (m 3) molars. The process extends down a little below 

 the alveolar border of m 2, and appears to be entire with an obtuse end. It is not so 

 long relatively, does not reach so low, as in Macropus major or Macropus {Osphranter) 

 robustus, but is more produced than in Macropus [Halmaturus) ualabatus: its propor- 

 tions are most nearly those of Macropus (Phascolagus) crubescens. The outer surface 

 of the base of the process is less deeply excavated than in any of the above-named recent 

 species. 



The convex tract behind the masseteric process and maxillary pier of the zygoma 

 leads into the orbit, and there, about 8 lines in advance of the hind border of the pier, is 

 the orbital aperture of the suborbital canal. It is single, subcircular, well defined, 

 without any appearance of the oblong depression we there see in Macropus, Osphranter, 

 and Halmaturus, where a second large foramen also communicates with the orbit. 



The floor of the orbit presents an oblong depression (the " entorbital fossa"), with 

 a snarp anterior and superior margin. From the fore part of this depression proceeds 

 the suborbital canal, commencing by a large circular hole (" entorbital foramen ") ; a little 

 way behind this is a smaller (" spheno-palatine ") foramen. 



The inner wall of the orbit, formed by the maxillary and palatine, curves outward 

 and upward from the upper border of the depression to unite with that in advance con- 

 tributed by the lacrymal, leaving the outer circumference of the entorbital foramen free 

 from any direct rise of the interorbital plate. Anterior to the entorbital canal there 

 is a more shallow and imperforate depression affecting the lower part of the lacrymal, 

 at a little distance from the anterior border of the orbit. This structure of the orbital 

 surface agrees with that in Macropus and Osphranter, with minor differences. 



In Macropus major the entorbital fossa is deeper, the sharp upper border being 

 extended backward beyond the spheno-palatine foramen ; there is a third smaller 

 ik pterygo-palatine " foramen at the end of that border ; but the fractured state of the 

 fossil prevents the determination of its agreement or otherwise in regard to that third 

 foramen. 



In Osphranter robustus the second foramen is as large as the first, and is situated to 



