THE VOYAGE OP THE * CHALLENGER.' 421 



The clavicles are always well developed, strongly convex forwards as 

 seen from the side, and forming a more or less widely-open U when seen 

 from in front. Their posterior ends are produced backwards to unite, by 

 ligament, with the acromial process of the scapula. The symphysis is 

 usually somewhat dilated and thickened and closely apposed to the 

 an tero- inferior angle of the sternum, to which it is connected by liga- 

 ment. In Pelecanotdes the clavicular arch is more V-shaped, its limbs 

 diverging but little, and the symphysis develops a firm articulation with 

 the carina sterni (vide PI. XXIII. figs. 3, 4) as in Phalacrocorax, Sula, 

 Plot>is, and Phaeihon of the Steganopodes. In the Oceanitidae (vide 

 PL XXIV. fig. 8) the symphysis fur culce has a strong, curved hypocleidial 

 process, directed downwards and backwards, very much more developed 

 than the corresponding part in any Procellarian genus, even Cymochorea 

 or Procellaria (t. c. fig. 6). 



Anterior Extremity. The humerus (PL XXI. figs. 1-3, where that of 

 Majaqueus cequinoctialis is figured) is long, with a cylindrical shaft, often 

 much compressed distally in such a way that the outer margin of the 

 bone with its condyle is anterior and the inner one with its condyle 

 posterior. The head is but little elevated above the general level of the 

 proximal end of the bone. The pectoral ridge is prominent and trian- 

 gular, but short, and the deltoid impression extends only as low as its 

 distal termination. Behind the deltoid impression is a linear one for 

 the latissimus dorsi. The bicipital surface is well developed, the lesser 

 trochanter strong and recurved ; it is excavated behind and below by a 

 deep infra-capitular fossa, bounded above by the strong interfossal ridge, 

 the supra-capitular fossa being a more shallow concavity. The tubercle 

 for the insertion of the pectoralis secundus is strong, and is situated at 

 the commencement of the pectoral crest, just anterior to the articular 

 head. Below and anterior to it is an oval depression, often large, for 

 the pectoralis tertius. The external condyle is prolonged obliquely 

 upwards and inwards on the anterior surface of the bone ; the capi- 

 tellum is distinct, and separated by a slight notch from the internal 

 condyle. The olecranar fossa is shallow and prolonged upwards into a 

 smooth, slightly excavated triangular area. The impression for the bra- 

 chialis anticus is deep and oval. 



Above the external condyle there is a very strong, forwardly-directed 

 epicondylar process, from which arises the more superficial of the bellies 

 of the extensor metacarpi radialis longior muscle. This is least developed Zool. Chall. 

 in Pelecano'ides and Thalassoeca. Exp. vol.^ir. 



The pectoral crest, on its inferior aspect, presents an elongated surface 

 for the attachment of the great pectoral, coextensive with the lower 

 moiety of its border. This surface develops a roughness at each 

 extremity, particularly below, where the main part of the more superficial 

 layer of the muscle is attached by its strong tendon. The double nature 



