438 ON THE PETRELS COLLECTED DURING 



t.p. Belly of tensor patagii muscles ; t.p.l. Their tendon, joined by b.s. (biceps 

 slip) formed by the humeral head of the biceps humeri muscle ; b. Main 

 belly of biceps muscle, formed by the coracoidal head ; 8. Body of sternum, 

 bare of muscular fibres. 



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

 layers of the pectoralis primus muscle (p. I a, p. 1 b), 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 ; 8. Sternum. (The line above 

 it shows the limit of origin of the deep layer of the pectoralis primus.) 



PLATE XVII. 



Fig. 1. 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} ; k. Its humeral head, which forms & biceps slip, joining the tendon 

 of the tensor patagii (t.p); p. 1. Insertions (cut) of the two layers of the 

 pectoralis primus muscle; e. Extensor; t. Teres; c.b.l. Coraco-brachialis 

 longus ; c.b.b. Coraco-brachialis brevis. 



2. Dissection of right wing of Ooeanites oceanicus, to show the peculiar expansor 



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

 (8.) ; e.s'. The other moiety, arising from the last scapular feathers (So.) ; 

 p. 1. Pectoralis primus muscle, to which the expansor secundariorum is 

 attached; H. Humerus; Pat. Patagial membrane; v.n. Yessels and nerves 

 to wing. 



3. Left shoulder-joint, inner side, of Tkalassiarcke 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. 



PLATE XVIII. 



E \\ -Fig- 1- Dissection of right elbow of (Estrelata lessoni, to show the disposition of the 

 pt. xi. pi. iv. tensor patagii muscles, as seen from above. 



2. The same in Ossifraga gigantea. 



3. Dissection of right wing of Majaqueus csquinoctialis, to show origin and general 



disposition of the tensor patagii muscles. Lettering as in PL XIX. fig. 2 ; 

 also t.p. Common belly of tensor patagii longus and brevis ; t.p.l . Cushion 

 of elastic tissue, developed in the tendon of the tensor patagii longus (t.p.l.) 

 at its origin from the humerus ; e. Elastic pad, developed in the marginal 

 tendon of tensor patagii longus, opposite the elbow ; d. Deltoid muscle ; l.d. 

 Latissimus dorsi (insertion) ; n> Circumflex nerve. 



PLATE XIX. 



Fig. 1. Dissection of right elbow of Prion desolatus, to show the disposition of the 



tensor patagii muscles, as seen from above. 



2. The same in Pelecano'ides urinatrix. H. Humerus ; 7?. Radius ; b. Biceps 

 muscle ; t.p.l. Tensor patagii longus ; t.p.b. Tensor patagii brevis ; e.m, e.m'. 

 Superficial and deep bellies of extensor metacarpi radialis longior ; e.m.* Inner 

 of twin tendons of origin of its superficial belly ; b.s. (in fig. 3). Biceps slip ; 



