Fig. 1. Left pectoral region of Majaqueus cequinoctialis, to show the double 

 pectoralis major {sett primus) muscle. Its superficial layer (p. la) has been for the 

 most part removed, its cut origin from the sternal crest and furcula (F.) being reflected : 

 p. la', its insertion into the humerus, also cut and reflected, p. lb. The deep layer, p. 2. 

 Fascia covering the 'pectoralis secundus muscle, t.p. Belly of tensor patagii muscles. 

 t.p.l. Their tendon, joined by b.s. (biceps-sli'p) formed by the humeral head of the 

 biceps humeri muscle, b. Main belly of biceps muscle, formed by the coracoidal 

 head. S. Body of sternum, bare of muscular fibres. 



Fig. 2. Dissection of left pectoral region of Diomedea brachyura to show the two 

 layers of the pectoralis primus muscle (p. la, p. lb), which have been cut and removed 

 in large part, and the compound pectoralis secundus. p. 2. Its sternal origin ; p. 2', its 

 coracoid origin ; p. 2", its furcular origin ; p. 2'", origin from coraco-furcular membrane 

 (c.f.m). p. 3. Pectoralis tertius. C. Coracoid bone. F. Furcula, at symphysis. S. 

 Sternum. (The line above it shows the limit of origin of the deep layer of the 

 pectoralis primus.) 



Fig. 3. Dissection of right wing of Oceanites oceanicus, to show the peculiar 

 expansor secundariorum muscle, e.s. Tendinous portion arising from the last remiges 

 (S.). e.s'. The other moiety, arising from the last scapular feathers (Sc). p. 1. 

 Pectoralis primus muscle, to which the expansor secundariorum is attached. H. 

 Humerus. Pat. Patagial membrane, v.n. Vessels and nerves to wing. 



Fig. 4. Left shoulder joint, inner side, of Ossifraga gigantea, to show the peculiar 

 biceps muscle, c. Its coracoid head, continuous below with the belly of the muscle 

 (b). h. Its humeral head, which forms a biceps-sli^, joining the tendon of the 

 tensor patagii (t.p). p. 1. Insertions (cut) of the two layers of the pectoral's 

 primus muscle, e. Extensor, t. Teres, c.b.l. Coraco-brachialis longus. c.b.b. Coraco- 

 brachial brevis. 



Fig. 5. Same parts in Thalassiarche culminata. c.,h. Coracoid and humeral heads 

 of biceps, here uniting below into the common tendon of that muscle (b.) b.s. 

 Biceps slip, largely tendinous and joining the tensor patagii near the elbow, derived 

 from the coracoid head of the biceps. 



