1905.] OSTEOLOGY OF THE EURYL.EMID.E, 55 



In the Eiuyliemidfe and Cotingida? — at least in so far as 

 Riqncola is concerned — the niajoi- portion is well developed, but 

 the brevis portion has now receded, not extending beyond the 

 middle of the humerus, and having an entirely fleshy insertion ; 

 the longus portion, on the other hand, is slender and terminates 

 in a long tendon. 



This interpretation of the transformations of the deltoides 

 viajor et minor, it Avill be noticed, runs directly counter to that of 

 Dr. Chalmers Mitchell, wdio, in a paper " On the Anatomy of 

 Gruiform Birds " (6), contended that apocentricity in this muscle 

 was shown by the gradual extension down the shaft of the major 

 portion. It would seem, rather, as if the archicentric condition 

 were represented by the maximum downward extension, and that 

 apocentricity is represented by the gradual reduction of muscular 

 tissue. 



That this reduction and inevitable suppression of the brevis 

 portion represents an extremely specialised condition there can be 

 no doubt ; and the fact that it is shared also by the Ootingidfe 

 seems to me, coupled with the numerous other points which these 

 two groups share in common, to show conclusively that the 

 Eurylfemida? and Cotingidae must henceforth be regarded as very 

 closely related forms. 



These two groups differ in some other myological charactei\s, as 

 might be expected. The most noticeable is the fact that the 

 latissimus dorsi jjosterior in the Cotingida? appears to be wanting, 

 though it must be remarked I have only been able to examine a 

 single specimen of Rupicola in this connection. In the Eurylse- 

 midae both muscles are present, strajD-shajDed in form, and widely 

 separated ; therein diftering from the Corvida?, in Avhich they are 

 of considerable size and slightly overlaj) one another. But this 

 feature is one of many piimitive characters which the Corvida? 

 have retained. 



The peculiar myological resemblances which these birds share 

 do not necessarily imply relationship ; but, as I have just remarked, 

 there are so many structures in which these two groups agree, 

 that it is impossible to entertain any notion of convergent 

 resemblance between the two. The points of likeness are so 

 peculiar, and affect such different, independent systems, that 

 correlated variation and convergence cannot be regarded as a 

 satisfactoiy explanation of the case. When two apparently con- 

 vergent forms come to be particularised, each new point of 

 resemblance which is brought to light is to be regarded as an 

 additional link in the chain of evidence, establishing the common 

 origin of the two forms in question. 



Thus, then, I contend there is no evidence which will justify 

 the present isolated position which has been almost universally 

 assigned to this gi-oup dui^ing the last few years. It is quite 

 possible that further investigation Avill show that the Eurylajmidte 

 are entitled to rank no higher than a subfamily of the Cotingida?. 



