:;:,s 



is Hat (/>), as in all the succeeding ribs possessing it ; anterior to this surface is a tubercle 

 for the attachment of the costal ligament. In the fifth rib (ib. fig. 9), besides the 

 process holding the same relative position to the tubercle as in the second rib, there is 

 another (/') at a greater distance, which answers better to the 'angle.' 



The neck (c) shortens as the ribs recede in position, and disappears with the loss of 

 the articular tubercle in the last three pairs. The longest ribs are the seventh and 

 eighth pairs in Phascolomys latifrons. The hind border of the proximal third of the 

 shaft is slightly produced, indicative of an 'intercostal groove.' The shaft is flattened 

 and expanded at its distal end (g and fig. 9'), which is twisted at right angles to the 

 broadest part of the neck of the rib. This terminal expansion (fig. 9') is lost in the 

 last three pairs (fig. 10). Six anterior pairs of rib-cartilages (PI. XCVIII. fig. 11, h, i-e) 

 articulate directly with the sternum, which consists of six bones, including the manu- 

 brium (m) and xiphisternal (x). The fourth and fifth sternebers coalesce earlier than 

 any of the others ; the articulation of the cartilages of the fifth pair of ribs ( 5 ) indicates 

 the place of the harmonia and the shortness of the fifth sterneber compared with the 

 rest ; its antero-posterior thickness is considerable, and increases as it recedes (as shown 

 in the side view (ib. fig. 11, a l). The cartilages of the sixth pair of ribs (h, 6) articu- 

 late to the lower angles ; and the inner or hind border alone affords attachment to the 

 xiphisternal (x). The manubrium (ib. fig. 11, m) is subcarinate, and affords oblong 

 syndesmotic surfaces for the strong clavicles. 



Phascolomys, like all the other genera of Marsupialia of which the vertebral formula 

 is known, has twenty-six vertebrae between the skull and sacrum. The nineteen ver- 

 tebra; following the seven cervical vary as to the number of the pleurapophyses deve- 

 loped as movably articulated ribs. In the two examples of Phascolomys platyrhinus of 

 which I have had the opportunity of examining the entire skeleton, fifteen vertebras 

 sustain such pairs of ribs, leaving four vertebras as 'lumbar;' and this was the formula 

 presented by the corresponding part of the vertebral column of the Phascolomys vombatus 

 described in my first memoir on Marsupial osteology 1 . In the only complete skeleton 

 of Phascolomys latifrons which has yet reached me the number of lumbar vertebras is 

 six. In this formula it deviates less from the rule of ' dorsal ' and ' lumbar ' vertebral 

 notation in the marsupial order than do the bare-nosed Wombats of Tasmania and 

 Australia. 



The number of vertebras which are confluent in the sacral region of Phascolomys 

 latifrons is four (PI. XCIX. fig. 1, s i-s 4), the two foremost of which articulate with 

 the ilia. The syndesmotic surface is formed on each side by an expansion of the hinder 

 half of the diapophysis of the first vertebra (ib. d l) and of the whole of that of the 

 second (d 2), forming together an oblong subreniform tract (ib. fig. 2) with an indication 

 of its division into two surfaces (d 1, d 2). The entire longitudinal extent of this joint is 

 1 inch 2 lines, with an extreme breadth of G lines. The diapophyses are confluent along 



1 Trans. Zool. Soc. vol. ii. p. 395. pi. lxviii. 



