BY VV. J. S. McKAY. 



265 



and myself, and published in a previous paper (22) : — " If the 

 views we have expressed are correct, then there can be little 

 difficulty in homologising the two forms of monotreme scapula. 

 In both forms the actual anterior border is meso-scapular. In 

 both the prescapular part of the bone is suppressed, though in 

 Platypus its site is still indicated by a ridge on the inner surface. 

 In both scapulfB the actual posterior border is really secondary, 

 being an exaggerated subscapular ridge, the subscapnlaris muscle 

 taking origin both from the ridge itself and the bone on both 

 sides of it. Finally, and in consequence of the last character, the 

 postscapular border is displaced outwards and exists as a mere 

 tricipital ridge upon the outer surface of the flat bladebone." 



Again, with regard to the humerus, the view that I have taken 

 with regard to its surfaces and borders will best be understood by 

 reference to Figs. 18 and 19 with the accompanying description. 



Lastly, I have found that many different formulae have been 

 given for the vertebrae and ribs of Echidna. I have collected a 

 number of these, which I give in the subjoined table. 



