377 



ON THE HOMOLOGIES OF THE BORDERS AND 



SURFACES OF THE SCAPULA IN 



MONOTREMES. 



By J. T. Wilson, M.B., Professor of Anatomy, Univ. of 

 Sydney, and W. J. Stewart McKay, M.B,, B.Sc. 



(Plate XXI.) 



There is not yet anything like a complete consensus of opinion 

 regarding the homologies of the borders and surfaces of the 

 monotreme scapula ; and indeed some very discrepant views have 

 been set forth by various anatomists. 



We shall not enter upon a description of the bone in detail, 

 since the accounts given in several of the works dealing with the 

 subject are satisfactory enough, and several of them are accom- 

 panied by figures (see list of references). It is with regard to 

 the interpretation of the parts of the bone that we propose to 

 offer a few observations. 



Our attention was directed to the subject during the coarse of 

 an investigation by one of us (M.) into the myology of the shoulder 

 region in Ornithorhynchus and Echidna, the results of which will 

 be published shortly. 



Ever since Owen (1) the actual anterior margin of the mono- 

 treme scapula [' margo anterior' of Meckel (2) ; ' bord anterieure' 

 of Cuvier (3)] has been generally recognised as the representative 

 of the free margin of the mesoscapula, i.e., as the free border of 

 an anteriorly projecting scapular spine. This interpretation has 

 at least been adopted by Flower (and Gadow) (4) and by Mivart 

 (5), and it is in our view undoubtedly correct, being well supported 

 by a study of the muscular attachments. 



