674 DR. P, CHALMERS MITCHELL ON THE 



to join the scapular heads near their tendon of insertion. The 

 external (text-fig. 125, S.C, p. 669) and internal scapular heads 

 arise from about the second fifth of the under surface of the 

 scapula, where they are separated by the insertion of the serratus 

 superficialis anterior. The three heads unite to form a strong 

 rounded tendon inserted to the median tubercle of the humerus. 



Ancoiiceus. 



Anconceus scapularis. — Origin by a strong forked tendon 

 from scapula' (text-fig. 125, A.S. 1, A.S. 2), passes into a rounded 

 muscular belly which sends an anchor to the humerus near the 

 insertion of the latissimus dorsi and receives a strong tendon 

 from the latissimus dorsi posterior. Passes into a strong flat 

 tendon just before reaching the elbow. 



Anconceus humeralis (text-fig. 125, A.H.). — Origin from the 

 whole length of the humerus, the origin being cleft proximally. 

 Passes into a tendon at the distal end of the humerus, and this 

 runs parallel with but united only by membrane to the tendon of 

 insertion of the anconseus scapularis. Insertion to the olecranon 

 of the ulna. 



The forked head of the scapular portion, the anchor to the 

 humerus, and the general relations of the two divisions of the 

 muscle are very much like what I have observed or find recorded 

 in Storks and Herons. The absence of any extension of the 

 scapular head to the clavicle or coracoid is rather a primitive 

 feature. 



Anconceus caput corcicokleum {Exjxmisor secunclciriorum) (text- 

 fig. 125, S.) — At the elbow there was a slip of muscular fibres 

 connected with the feathers and giving rise to a very delicate 

 tendon which I traced up the under surface of the skin close to 

 the anconceus, but which then appeared to become diffuse and be 

 lost in the subdermal fasciae. There was no trace of it passing 

 through the edge of the teres major, as usually happens when it 

 is well developed, or in the axilla. 



This was one of the muscles to which Garrod paid great atten- 

 tion, hoping to find it iiseful in classification, but further obser- 

 vations have not justified his anticipations, as it is present or 

 absent in very closely allied birds. It is usually absent in 

 Steganopods, but present in a few cases. It is present in Storks, 

 and in Herons except ArcleMa and Cancroma. According to 

 Beddard it is absent in Scopus. Its vestigial presence in Bcdceni- 

 ceps is therefore interesting but of no systematic value. 



Pectorcdis thoracicus. — The great pectoral (text-fig. 126, Pec, 

 p. 671 ; text-fig. 128, Pec.) in Bcdceniceps is an enormous mass of 

 muscle arising from the clavicle, the membrane between the clavicle 

 and coracoid, from the whole of the keel and from all the posterior 

 part of the sternum with a considerable overlap to the ribs. I 

 could not trace any definite horizontal division of the muscular 

 mass. The insertion is by two very distinct tendons, which 

 cross each other in a remarkable fashion. The greater and more 



