422 O5 THE PETRELS COLLECTED DURING 



of the pectoral muscle is indicated by a distinct muscular ridge dividing 

 the general area of insertion into two. 



In the Oceanitidse the humerus is conspicuously a stouter and shorter 

 bone, with its shaft evidently curved, instead of being almost straight, 

 The epicondylar process projects much less forwards, and is continued 

 down by an elevated ridge to the surface of the condyle itself. 



In the Albatrosses the humerus is distinctly concave forwards, with its 

 shaft considerably compressed throughout. The pectoral crest is sharply 

 pointed, the bicipital surface very prominent and convex, the internal 

 trochanter less developed, and the infra-capitular fossa very shallow, 

 with its apex occupied by a large pneumatic foramen, and the brachialis 

 impression long and very shallow. 



In Pelecanoides, as might have been expected from its diving habits, 

 the humerus is somewhat modified from the ordinary Procellarian type. 

 The shaft of the bone is comparatively short and much compressed, 

 especially below, where it has sharp anterior (external) and posterior 

 (internal) margins. The pectoral crest is little developed. The internal 

 condyle descends considerably lower than the external one, and the capi- 

 tellar surface is well developed and compressed. Behind it and the 

 external condylar trochlea is a strongly-marked deep pit, into which fits, 

 like a peg, a sharp conical process developed at the proximal end of the 

 ulna. The epicondylar process is very short, and the depression for the 

 brachialis anticus very shallow. 



The radius is a slender, straight, and cylindrical bone, with its distal 

 end depressed and grooved superiorly. 



The ulna is much stouter, with its posterior edge sharply keeled, with 

 only slight impressions for the secondary remiges. The olecranon 

 process is short and bluntly triangular. In Pelecanoides the radius and 

 u'lna are considerably compressed from before backwards. The ulna is 

 stout, and develops at its proximal end a slightly curved triangular 

 process, directed upwards, which, as already described, fits into a cor- 

 responding socket on the humerus, and so firmly unites the bones together. 

 The manus is very long. The second and third metacarpals are nearly 

 parallel and straight, the third metacarpal being much more slender than 

 its fellows. The pollex has but one phalanx, which is strong and long, 

 about equalling one half of the second metacarpal. The two phalanges 

 of the index are well developed, the basal one, which does not articulate 

 with the third digit, being much dilated posteriorly. 



ZooL jCh9.ll. In the Oceanitidse the radius and ulna are generally stouter and 

 Exp. vol. iv. granger bones than they are in the Procellariidae ; the former is*considerably 

 pt. xi. p. . ex p an( j e( j a t its distal extremity. 



As may be seen by the table at the end of this section (p. 426) the 

 three chief segments of the fore limb are, as a rule, nearly equal in length, 

 this being especially true as regards the arm and forearm. 



