102 THE VOYAGE OF H.M.S. CHALLENGER. 



in different members of the group of Spheniscidse, it may be useful to summarise tbe 

 distinctive characters of that group, so far as these muscles are concerned, by a brief 

 enumeration of the peculiarities which the muscles present in the Spheniscidse, as compared 

 with other birds. This, I feel, I cannot do more effectively or tersely than by quoting 

 the follo-^dng paragraph from the oft-referred to monograph on the Osteology and 

 Myology of the Spheniscidae of MM. Gervais and Alix. 



In translating this paragraph I have, for the convenience of future workers in the same 

 field, inserted within brackets the synonymes used in the foregoing pages to designate 

 the muscles referred to by MM. Gervais and Alix. 



The peculiarities of the muscular anatomy of the wdug in the Spheniscidae may be 

 summed up as follows : — 



" The absence of the brachial biceps, brachialis anticus, pronator teres, pronator 

 quadratus, short muscles of the thumb, and of the costal portion of the tensor membranse 

 axillaris (dorsal cutaneous) ; the atrophy of the infra-spinatus, and the coincident absence 

 of a humero-scapular bone ; the atrophy of the extensors and flexors of the hand ; the 

 feeble development of the cubitalis anterior (flexor carpi ulnaris) the proximal extremity 

 of which does not pass round the epitrochlea and is not provided with a sesamoid ; the 

 insertion of the angularis (levator anguli scapulae) into the deeper surface of the 

 scapula ; the great development of the trapezoid fascicle (portion A.) of the latissimus 

 dorsi, its termination by means of a separate tendon, and the presence of a fibrous ring 

 through which that tendon passes along with that of the latissimus dorsi proper (portion B.); 

 the presence of an external fascicle (fii'st head of triceps) belonging to the long portion 

 of the triceps arising from the clavicle, and the great strength of that fascicle ; the presence 

 of two large sesamoid bones behind the elbow joint, of which one receives the tendon of 

 the vastus internus (third head of triceps), and the other those of the vastus exteruus 

 (fourth head of triceps) and of the long head (second head of triceps) ; the disposition of 

 the short flexor of the forearm (brachialis internus) ; the great strength of the accessory 

 subscapular muscle (coraeo-brachialis) ; the adhesion to the middle pectoral (pectoralis 

 medius) of the coraeo-brachialis (pectoralis minor) which in other birds does not reach 

 the sternum ; the large size and thickness of the great pectoral (pectoralis major), composed 

 of very oblique as well as of transverse fibres ; its insertion into the inner surface of the 

 humerus, and the strength of its accessory cutaneous muscle (muscle des parures); the 

 enormous strength of the middle pectoral (pectoralis medius), and its division into two 

 parts as in the Gallinacese and Tinamidas, a character which distinguishes the Spheniscidae 

 from all Palmipedes, at the same time that it is common to the Grebes, Eails, and wading 

 birds in general. 



" It is necessary to observe, on the other hand, the development of the great abductor 

 of the thumb (extensor metacarpi radialis brevis), as well as of the adductor of the hand 

 (flexor brevis metacarpi), characters which approximate the Spheniscidae to the Ostriches." 



