222 



ME. P. CHALMERS MITCHELL ON SO-CALLED 



anconeus (D. 3) is partly fused with it, althougli it has a separate 

 insertion. In C and a (fig. 4, III) the final stage has been 

 reached. The dista] parts of the long division of the muscle have 



D.1 



- D.3. 



Deltoid es muscle. 

 PAT. Delt. patagLalis. S. Tendon of Supracoracoideus. D. Deltoides major. 



A. Aneonteus soapularis. 

 I. Columba livia. II. Columhida pictci. III. Geopdia tranquilla. 



apparently quite disappeared, but are represented actually by 

 small slips which leave respectively the distal ends of the deltoides 

 patagialis and the anconseus to be inserted on the distal end of 

 the humerus on either side of the radial nerve. Thus all the 

 eutaxic pigeons show extreme development of this muscle. In 

 six of them it has passed beyond the development into stages of 

 degeneration. It is interesting to notice that in the Passerines 

 there is usually a similar complete division of the deltoid, but I 

 do not know of the existence of stages of degeneration of the 

 long division. 



M. metapataqiaUs or Expansor secundariorum. — This curious 

 slip, upon which so much stress was laid by Gairod, is obviously 

 decaying among pigeons. In Columba liiia it is extremely 



