808 DR. J. MURIE ON PHASCOLOMYS PLATYRHINUS. [June 27, 



same specimens. In P. latifrons the same flattening underneath of 

 the bodies of the lumbar vertebrae occurs as in the dorsal region, but 

 the bodies altogether seem stronger than in similar-sized Wombats. 



In P. platyrhinus the transverse processes of the lumbar vertebrae 

 are immensely long. The first and last are shorter than the two 

 middle ones. The hindmost three are wider than the sacrum. 

 Compared with those of P. latifrons they are narrower antero-poste- 

 riorly and somewhat rounder. The size being less in P. wombat, 

 they otherwise correspond to what has been said of P. platyrhimis. 



All the examples of P. latifrons, none of P. platyrhimis, and only 

 one of P. wombat exhibited short suturally connected pleurapophy- 

 ses resting upon the diapophyses of the first lumbar vertebrae. 



If other proof were wanting of the termination of the dorsal and 

 commencement of the lumbar vertebrae in P. latifrons, the presence 

 of these pleurapophyses in P. wombat, where fifteen ribs exist, would 

 satisfy objections which might be raised, that in P. latifrons their 

 more regular occurrence indicated a greater number than thirteen 

 ribs as the normal condition. 



Sacrum. — In defining the number of sacral vertebrae present in 

 specimens of the Common Wombat, Prof. Owen remarks*, " If we 

 regard those vertebrae only as sacral which join the ossa innominata, 

 then there are but three" — more often, it will be found, only two. 

 If, on the other hand, anchylosis is the test, then the sacral vertebrae 

 may vary from 3 to 4-5, or even as many as 7, in number in different 

 specimens. I am inclined, however, to agree with a further state- 

 ment of the same anatomist, that four are the normal number of 

 bones (Cat. Coll. Surg. p. 330). 



Besides the fact that the four vertebrae succeeding the lumbar 

 ones have transverse processes directed almost straight outwards, or 

 the posterior two of them even somewhat forwards, in contradis- 

 tinction to the vertebrae behind, which have transverse processes in- 

 clined at an angle backwards, there is the still more cogent reason, 

 that the sacral plexus passes through the three foramina, bounded 

 by the usually coalesced four sacral elements. 



This division between true sacral and caudal vertebrae is remark- 

 ably well seen in specimens of P. latifrons, where the transverse 

 processes are shorter and less liable to anchylosis than in either of 

 the other species. 



The sacral vertebrae of P. platyrhinus are chiefly distinguishable 

 from those of P. wombat by the greater width of the transverse pro- 

 cesses and by their unusual flatness both on the pelvic and dorsal 

 surfaces. The extent of the auricular surface abutting against the 

 ilia is relatively greater ; and, as compared with most specimens of P. 

 wombat, the base of the sacrum and anterior edge of the first trans- 

 verse process reach somewhat further forwards on the ilia. These 

 conditions appear to give greater lateral and longitudinal capacity to 

 the cavity of the pelvis ; indeed it is the width and flattening 

 of the dorsal surface of the sacral region of the pelvis continued 

 backwards towards the tail which produces the characteristic hinder 

 * Trans. Zool. Soc. vol. ii. p. 39G. 



