360 SHOULDER-GIRDLE IN MONOTREMES. 



to the anterior portion of the M. deltoid, and to the M. 

 pectoralis major. kV. N. to the M. latissimus dorsi. md. 

 N. medianus. Phr. N. phrenicus. Pt', N. to M. pectoralis 

 major and to the integument or panniculus. r. the largest 

 branch from N. radialis. r' N. to the integument from 

 which a branch Lr' springs to supply M. latissimo-condy- 

 loideus. r" N. to scapular belly of the M. triceps. r s. 

 nerve cord which supplies branches to M. subscapularis and 

 M. infraspinatus. <SV^. N. to the M. subclavius. S.M. 

 N. to serratus magnus. SS. Nn. subscapulares. u. N. 

 ulnaris. 



Fig. IS. — Humerus of Echidna (right side). The antero-interual and 

 antero-external surfaces are shown. The sharp supi- 

 nator ridge (Sp. R.) is seen running up from the external 

 condyle {Ex. C.) M. S. indicates the musculo-spiral 

 groove. The large bicipital groove (Br. 6'.) is also shown. 

 Ex. B. is the external boi-der continued into the pectoro- 

 deltoid ridge {P. D. ) at the proximal end and the supinator 

 ridge at the distal end. A. B. would represent the 

 anterior border of the bone. G.T., L.T. greater and 

 lesser tuberosities. F.Sc. Foramen supraeondyloideum 

 (The outline of this figure and the next are from Westling). 



Fig. 19. — This shows chiefly the boundaries of the posterior suiface. The 

 supinator ridge is seen to terminate before it reaches the 

 proximal extremity of the humerus (in Ornithorhynrhus it 

 does not), and the dotted line running between the supina- 

 tor ridge and the external border indicates that the pectoro- 

 deltoid ridge, though apparently continued into A.B., 

 should morphologically be considered to take the direction 

 of the dotted line in Fig. 19, that is, across the musculo- 

 spiral groove to the supinator ridge (Sp. R. ). 



