1898 - 99 .] Dr E. Broom on Marsupial Shoulcler-Girdle. 483 
the bulbous end of the coracoid. By the time the foetus is 23 mm. 
in length, the girdle is quite detached. 
In the Pseudochirus foetus of 16 mm., the coracoid, though in 
contact with the presternum, is not structurally continuous with 
it. 
In the early foetus of Petrogale (21 mm.) the coracoid is of very 
large size, and is continued backwards for some distance by the 
side of the first rib. It is for a short distance structurally con- 
tinuous with the sternum. In this foetus no distinct omosternum 
can be detected. 
In considering the morphology of the scapular borders, the 
following conclusions are arrived at : — 
(a) That the spine proper, having no cartilaginous basis, is 
the homologue of the cleithrum or epiclavicle of the lower 
Theromorphs. 
(b) That in the Monotremes there is no supra-spinous fossa, 
owing to the spine or cleithrum being applied to the morphological 
anterior border ; while in the higher mammals a supra-spinous 
fossa has been formed, owing to the spine becoming applied to 
the outer surface of the scapula, and away from the anterior 
border. 
With regard to the coracoidal elements, the following are the 
principal conclusions arrived at : — 
(a) That the well-developed coracoid in the foetal marsupials, 
and, consequently, the coracoid process in the higher mammals 
generally, is the homologue of the posterior coracoidal element in 
the Monotremes and Theromorphs, and of the coracoid in Eeptiles 
generally. 
(b) That the anterior coracoidal element (“ epicoracoid ”) in 
Monotremes and Theromorphs is the homologue of the precoracoid 
of the Amphibia. 
(c) That the only representative of the precoracoid remaining in 
the higher mammals is the coraco-clavicular ligament. 
The cartilage which forms round the ends of the clavicle is 
regarded as of a secondary nature, and of no special morphological 
significance. 
