346 PEOPESSOR OWEN ON THE SPECIES OF PHASCOLOMTS. 



zoologists generally is the more probable since the grand ' Osteographie ' of De 

 Blainville was interrupted by the regretted demise of the indefatigable author before 

 it had reached his subclass Didelphys'. 



§2. Cranial Characters of Vhascolomys. 



The characters of the skull of Phascolomys platyrhinus, briefly defined in the 

 ' Descriptive Catalogue of the Osteological Series in the Museum of the Royal College 

 of Surgeons' ^, have subsequently been determined by Prof. M'Coy^ and Dr. Murie* to 

 be those of the continental or Victorian bare-nosed, large, brown or black Wombat. 



A skull of this species, figured of the natural size in Plate LI. fig. 1, gives a length, 

 from the hindmost ridge of the occiput to the front border of the incisor-alveoli, of 

 8 inches. Another skull in the British-Museum collection exceeds this only by one 

 line ; a third is in the same slight degree smaller. The specimen submitted to me by 

 Dr. McBain of Edinburgh, in 1855, yielded a length of 8 inches; two other specimens 

 have the length of 7 inches 8 lines (PL L. fig. 1), and 7 inches 6 lines (PI. LII. fig. 1). 

 Dr. Murie gives minor dimensions of some, probably female, sf)ecimens '. 



The occiput (Plate L. fig. 1, 2, 3, & fig. 2) rises vertically from the foramen magnum 

 at the median line, but curves a little backward laterally, where it forms the 

 sides of the broad superoccipital (ib. fig 2, 3). The lower and lateral parts of the 

 occiput are formed by the exoccipitals (ib. fig. 2, 2), the mastoids ( 8 ), and squamosals (27). 

 The occiput is higher in proportion to its basal breadth than in Phascolomys vomhatus 

 (ib. fig. 3) ; it is more quadrate in form ; it does not curve upward and inward so regularly 

 from the mastoid processes (8) to the summit, as in Phascolomys latifrons (ib. fig. 4). 



The composition of the occipital region agrees Avith that illustrated in PI. Ixxi. 

 fig. 6 (Trans. Zool. Soc. vol. ii.), in Phascolomys vomhatus. But the portions con- 

 tributed by the squamosals (PI. L. fig. 2, 27,27), do not reach so low down upon the 

 mastoid process as in Phascolomys vomhatus (figs. 3, 6, 27, 8j. The basioccipital 

 (PI. LII. fig. 1, 1) contributes about half an inch of the thick lower border of the 

 foramen magnum. The exoccipitals (PI. L. fig. 2, 2) form the lateral borders, de- 

 veloping there the condyles ; and the superoccipital completes the middle of the upper 

 border, which is sharp ; and as ossification of the latter element does not usually 

 extend so low down as to fill up the whole interspace left by the exoccipitals, the 



' The ' Prospectus ' of this work was issued after the reading of my first memoir on the osteology of the 

 Marsupialia ; see Zool. Trans, vol. ii. p. 379. The character and form of the work, especially the richness 

 and beauty of its illustrations, exemplified in the Part which appeared after the communication of my 

 second memoir, led me to abandon that subject, as being likely to meet with more complete illustration in 

 the ' Osteographie du Squelette et du Systeme Dentaire des cinq Classes d'Animaux Vetebres reoents et fossUes,' 

 4to, Paris, 1840-1860. 



= 4to, 1853, vol. i. p. 334. no. 1841. 



' Transactions of the Eoyal Society of Victoria, vol. viii. (1868), p. 267. 



• Proceedings of the Zoological Society of London, Dec. 1865, p. 838. ' Ibid. p. 845. 



