[483] 
XV. On the Osteology of the Marsupialia. (Part IV.) Bones of the Trunk and Limbs. 
Phascolomys. By Professor Owen, C.B., F.R.S., ZS. 
Read 3rd December, 1872. 
[Puates LXIX. to LX XIV. | 
THE endeavour to restore the lost species of Wombat presumes a power of recognizing 
the bones or portions of bones when discovered in a fossil state; and this can only be 
acquired by a knowledge of the characters of the corresponding bones of the existing 
species. 
Such knowledge has been imparted, in reference to the skull of Phascolomys, in my 
former Papers; I propose to make the remainder of the skeleton the subject of the 
present ‘ Part,’ in which the descriptions and figures are limited to those bones of the 
trunk and limbs yielding satisfactorily distinctive and determinative characters subser- 
vient to the above-defined aim. 
Vertebral Column.—The general characters of the vertebral column in the genus 
Phascolomys are defined in my first memoir’. The annular atlas is there shown, from 
a specimen (of Phascolomys vombatus) in the Museum of the Royal College of Surgeons 
of England, to have the lower part of its ring “ completed by dried gristly substance,” 
not, as in some kinds of Kangaroo, by “ extension of ossification from centres in the 
superior lamine”’. The term ‘neurapophysis’ had not then been proposed for these 
vertebral elements, nor had I, in 1838, satisfied myself that the ‘centrum’ of the atlas 
was the ‘odontoid process’ of the succeeding vertebra. It is further remarked that 
“the transverse processes are grooved merely by the vertebral arteries,” and that “ the 
atlas presents only the perforation on each side of the superior [now called ‘neural | 
arch’’’, 
These general characters of the atlas of the bare-nosed Wombat of Tasmania are 
repeated in that of a not fully grown specimen of Phascolomys platyrhinus (P1. LXIX. 
figs. 3 & 4); but in the atlas of an older and larger specimen of that species ossification 
has extended into the sclerous representative of the pleurapophysis, and has converted 
the vertebrarterial notch into a foramen on both sides (as indicated by the dotted line, 
p/, in fig. 3, Pl. LXIX.). 
The same bony circumscription obtained on the right side in the atlas of a Phasco- 
lomys latifrons (Pl. LXIX. figs. 1 & 2, pl), The first cervical nerve, in both species, 
1 “On the Osteology of the Marsupialia” (Part I. 1838), Trans. Zool. Soc. vol. ii. p. 379 et seq. 
* Th. ib. p. 394. I haye since seen the atlas of an old male Macropus rufus, incomplete below. 
* Tom. cit. p. 394. 
