SHOULDER-GIRDLE IN DASYURUS AND PERAMELES. 453 
coracoid alone, and I have seen no reason to alter my opinion. 
The precoracoid is apparently quite lost as a cartilage, but is 
probably represented by the coraco-clavicular ligament. 
In the previous paper on the marsupial girdle (2) it was 
suggested, as a possible explanation of the development of the 
scapula with three borders from the ancestral form which had 
only two, that the spine was a new formation arising from the 
shifting of the cleithrum from the anterior border to the outer 
side of the blade. Though the spine itself can hardly be 
regarded as the homologue of the cleithrum, it is possible that it 
replaces the cleithrum, and has its position determined by the 
pre-existing bone. The condition of the scapula in the fcetal 
Dasyure suggests an alternative possible expJanation, as here the 
spine arises from the anterior border of the scapula, and the 
“prescapula” is a new formation. The difference in the two 
conditions may be due to the fact that in the Diprotodont 
the spine, by being to some extent on the side of the blade, 
leaves a distinct prescapular fossa in front; while in the Dasyure 
owing to the spine being attached to the anterior border of the 
cartilaginous blade, a prescapular fossa has to be formed by 
a new bony development. In the ossification of a cartilage it is 
exceptional for the bone to leave the limits defined by the 
cartilage, but another instance of it occurs in the development 
of the marsupial alisphenoid. 
Papers referred to in the Text. 
1. Broom, R.—‘“On the Existence of a Sterno-coracoidal Articu- 
lation in a Foetal Marsupial.” Journ. Anat. & Phys. 
vol. xxxix. p. 513 (1897). 
2. Broom, R.—‘ On the Development and Morphology of the 
Marsupial Shoulder-girdle.’ Trans. Roy. Soc. Edinb. 
vol. xxxix. pt. il. no. 29 (1899). 
3. Hixt, J. P.—‘ On the Foetal Membranes, Placentation, and 
Parturition of the Native Cat (Dasyurus viverrmus).” 
Anat. Anzeiger, xvii. p. 364 (1900). 
4, Hiun, J. P.—‘Contributions to the Embryology of the 
Marsupials: II. On a further Stage in the Placentation of 
Perameles.” Qu. Journ. Mier. Sci. vol. xlui. 1899. 
