138 ON THE HOMOLOGIES OF CERTAIN MUSCLES 



DESCRIPTION OF PLATE 3. 



Fig. i. Scapulo-coracoid arch of Crocodile (Crocodilm vulgaris). 

 8C. Scapula. cr. Coracoid. gl. Glenoid cavity. 

 be. Facet of origin of biceps. Round this portion of the coracoid the head of the 



* epicoraco-humeral ' muscle which comes from the inner surface of the scapula 



winds. 

 'per. Praecoracoid. The surface whence the coracoid head of the 'epicoraco-humeral' 



muscle arises extends from the point lettered per up to the line of fissure between 



scapula and coracoid, and a little beyond it. 

 d. Ridge on scapula, giving origin to deltoid. tc. Facet of origin of triceps. 

 88. Surface of origin of supra spin atus. erf. Coracoid foramen. 



Fig. 2. Scapulo-coracoid arch of Emu (Dromaius novae hollandiae). Adult. 



sc. Scapula. cr. Coracoid. gl. Glenoid. per. Praecoracoid. 



cla. Line of clavicular abutment on scapula. 



Between the points -per and gl, and below cla, lies the praeglenoid expanse, made 

 up by factors both from scapula and coracoid. From this expanse the coracoid 

 head of the epicoraco-humeral muscle takes origin. The deltoid takes origin 

 from the scapula immediately above and behind the line cla. 



Fig. 3. Muscles in connexion with the scapulo-coracoid arch and upper extremity of 

 Crocodile (Crocodilus biporcatus). The same arrangement has been noted in 

 Alligator lucius, with scarcely any differences. 



pm. Pectoralis major. The muscle has been divided, and its origin from the 

 sternum and interclavicle turned mesially, and its tendon of insertion into the 

 greater tuberosity of the humerus turned outwards, p m', tendon of pectoralis 

 major. 



eh. 'Epicoraco-humeral' of Mivart ('Trans. Linn. Soc.' vol. xxv. 1866, p. 383), a 

 bicipital muscle ; its inner head winds round the coracoid face of the praeglenoid 

 expanse, to take origin from the visceral surface of the scapula ; its outer head 

 arises from the praecoracoid, and, to a small extent, from the praescapular portion 

 of the praeglenoid expanse, where it is in close relation with the deltoid. The 

 inner of these two heads is intimately connected at its insertion with that of the 

 pectoralis major, and, together with the tendon from the other head, occupies on 

 the humerus a position between that of the tendon of the deltoid externally and 

 inferiorly and that of the pectoralis major internally and inferiorly. The in- 

 sertion of the omohyoid corresponds with the origin of the praeglenoid head of 

 the epicoraco-humeral ; and the fibres of the two muscles are, to some slight 

 extent, continuous with each other, at least in young specimens. 



e i. Muscular fascicle which arises from second sternocostal cartilage in the same 

 series as the external oblique and intercostals, but which may also be looked 

 upon as homologous with an anterior segment of the ' rectus abdominis,' which 

 is often not distinguishable from the former of these muscles. It ends in a 

 delicate tendon, which loses itself, along the coracoid groove, in the sternum and 

 the origin of the pectoralis major. The rectus abdominis in many ordinary 

 mammals has an insertion into the first rib (see Professor Turner, ' Journal of 

 Anatomy and Physiology,' May 1868, p. 393), from which the ordinary mam- 

 malian subclavius arises ; and in the order Monotremata it has, in both species of 

 Echidna and in the Ornithorhynchus, an insertion into the coracoid at no great 

 distance from the area of origin of their epicoraco-humeral, which I hold to be 



