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Genus Phascolomys. 



Extinct Species resembling the existing ones in size. 



§ 1. Introduction. — To facilitate the comprehension of the characters, deduced from 

 fragmentary fossils chiefly, of the extinct Wombats, I premise a brief recapitulation of 

 those of the skull of the existing kinds which bear most closely on the smaller fossil 

 species to be described in the present section. 



I propose, first, to point out, as far as materials permit, the amount of variety to which 

 the same species of Wombat may be subject in the nasal bones, — a requisite preliminary 

 to determining the value of these bones in differentiating recent and fossil species of 

 Phascolomys. 



§ 2. Nasal bones in Phascolomys vombatus, Per. — In an old male Tasmanian Wombat 

 (Phase, vombatus) the basal breadth equals two thirds of the length of the pair of nasal 

 bones. The outer angles of the nasals, at their base (is), are divided from the lacrymal 

 tubercle (73) by a strip of maxillary (21) 4 lines in breadth, joining to that extent the 

 frontal (n). The sides of the pair of nasals converge forward at the hinder third, then 

 run parallel, gently curving inward, and finally gaining the margin of the nostril, 

 with a slight curve outward. Thus the course of each lateral border of the nasals is 

 undulate. Their tips (15 ) extend forward about three lines in advance of the naso-pre- 

 maxillary suture, and are bevelled off to an obtuse point from without obliquely inward 

 and forward. Together these bones form the middle third of the upper border of the 

 external bony nostril. The frontals (n) make a slight projection into the middle of the 

 fronto-nasal suture, which from this shallow indent runs outward and a little forward 

 to the nasal process of the maxillary (21)*. The naso-maxillary suture forms the hind 

 fifth part of the lateral border of the nasals ; the naso-premaxillary suture runs along 

 the rest of the extent of the nasal bones ; i. e. to the beginning of their free ends, 

 which are short and subobtuse. 



In a second Tasmanian Wombat the nasals (fig. 1, 15) differ from those above described 

 in their basal breadth, this being equal to rather more than three fourths of their length, 

 or as 77 to 100, also in the absence of any mesial indent of the fronto-nasal suture, and 

 in the sharper convergence forward of the hinder fourth part of the lateral margins. 

 These margins describe a similar wavy course, convex outwards along the middle third, 

 or a little in advance of it. The apices overhanging the nostril are less sharp and pro- 

 minent than in the last or type specimen. 



* This specimen, figured in the 'Transactions of the Zoological Society,' vol. ii. 1838, shows the usual 

 characters and is not here repeated : the references to the numerical symbols of the bones, in aid of the 

 description, are seen in the subjects of the two Woodcuts showing the varieties. 



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