358 Transactions of the South African Philosophical Society. 



When the ancestor of the ostrich became a flying bird the coracoid 

 would become elongated to accommodate a large pectoral muscle, 

 and there would, doubtless, be a large clavicle. The 10-day embryo 

 still shows evidences of the flying ancestor in the well-marked angle 

 which there is between the scapula and coracoid. As the power of 

 flight became lost the clavicle disappeared. "We find in the emu a 

 shoulder girdle something like that which the primitive ostrich prob- 

 ably had before it completely lost the clavicle. As the clavicle 

 disappeared its place was to some extent taken by the anterior 

 process of the scapula, which gave a better protection to the front of 

 the chest than the loose clavicle. There seems to me to be no evidence 

 that the anterior process of the scapula is in any sense homologous 

 with the precoracoid of the early reptiles. In a number of the 

 higher Sauropsida the need for an anterior ventral bar to the 

 shoulder girdle occurs, and in each the requirements are fulfilled 

 by a process from the scapula. Thus in the Chelonians we get an 

 enormous ventral scapular development, and in the Plesiosaurs the 

 ventral development of the scapula is usually even greater than the 

 dorsal. 



Anteeior Limb. 



In the 10-day embryo the skeletal structures are first beginning 

 to become distinctly chondrified, and only the larger elements can 

 be made out with certainty. The radius and ulna are short, stout 

 parallel bars, which are well differentiated. The carpus is repre- 

 sented by a large mass of precartilage in which is very clearly 

 differentiated a large ulnare and less clearly a large distal element, 

 which is probably the combined carpalia 1, 2, 3. The metacarpus of 

 the pollex is very imperfectly defined, but the second and third 

 metacarpals are well developed and quite distinct;. There is a short 

 but quite distinct fourth metacarpal. In fact the fourth metacarpal 

 is very much more distinct than the first. 



In the 11-day embryo most of the elements are well defined. 

 The radius and ulna are large and of about equal size. In the 

 carpus there are three well-defined elements — a very large radiale, a 

 large distal element evidently the combined carpalia 1, 2, 3, and a 

 small but very distinct ulnare. Four metacarpals are seen. The 

 first, second, and third are all of large size, and developing phalanges 

 can be seen on the distal ends of each. The fourth metatarsal is of 

 small size, but still quite distinct. 



In general appearance the manus is somewhat like that of Apteryx 

 as figured by Jeffery Parker. In judging from one or two of his 

 figures, one is inclined to think that probably the two forms resemble 



