BY W. J. S. McKAY. 287 



panuicuhis as in Didelphi/s and Phalangista ; and a condition (b) 

 such as I find in Notoryctes in which the P. quartus is only repre- 

 sented by a thickened portion of the humeral panniculus over- 

 lapping, it may be, the latissinms docsi. The intermediate 

 conditions (c) exhibit variously differentiated abdomino-humeral 

 pannicular, or laterally placed " pectoralis quartus," slips. And 

 in this connection may be quoted Professor Cunningham's opinion 

 in reference to axillary muscles generally, that "in the region of 

 the axilla there is not the same sharp well-defined subdivision 

 between the panniculus and the deeper stratum that exists else- 

 where." 



P. MINOR. 



Although the pectoralis minor has been mentioned by some 

 observers, such as Meckel, Owen, Cuvier and Laurillard, and Coues, 

 it does not appear that there is any muscle present that really 

 represents a true pectoralis minor. The muscles that have been 

 put forwaixl as representatives of the P. minor, are the costo- 

 coracoid, the sterno-epicoracoid, and the epicoraco-humeral. We 

 shall see, however, when considering these various muscles, that 

 other and more probable homologies have been assigned to them. 

 {Vide also remarks by Humphry under M. epicoracoideus.) 



M. EPICORACO-HUMERALIS. 



EcHiDXA : M. supracoraroideus, Fiirbringer, Westling ; Epicoraco- 

 humercd, Mivart, Leche. 



Ornithorhyxchus : Anterior part of deltoid, Meckel, Owen, Coues; 

 Supracoracoideus, Westling, Fiirbringer; Epkoraco-hiimercU, Leche; Moyen 

 petit pectoral, Cuvier and Laurillard. 



Echidna. 

 Origin. The muscle is displayed (covered by a well-marked 

 layer of fascia), when the anterior part of the P. major and the 

 clavicular deltoid are reflected. It arises from the whole of the 

 ventral face of the epicoracoid (with the exception of a small area 

 situated postero-internally, and giving origin to the epicoracoid 

 head of the biceps). (Fig. 4, Fp. H.). 



