REPORT ON THE ANATOMY OF THE PETRELS. 49 
The scapula is a slender, slightly curved bone, presenting no special peculiarities. Its 
acromial process is prolonged inwards and forwards to nearly, or quite, meet the posterior 
end of the clavicle. The angle it forms with the coracoid varies very much in different 
genera, beg most acute in Pelecanoides, whilst in the Oceanitide it is hardly, if at 
all, less than a right angle (vide Pl. VIL. fig. 8, Fregetta). Procellaria and Cymochorea 
resemble the other Procellariidze, the coraco-scapular angle being in them obviously 
(t.c., fig. 6) acute. 
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 antero-inferior angle of the sternum, to which it is connected by ligament. 
In Pelecanoides the clavicular arch is more V-shaped, its limbs diverging but little, and 
the symphysis develops a firm articulation with the carina sterni (vide Pl. VII. figs. 
3, 4) as in Phalacrocorax, Sula, Plotus, and Phaéthon of the Steganopodes. In 
the Oceanitide (vide Pl. VII. fig. 8) the symphysis furcule 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 
(¢.¢:; fig. 6): 
Anterior Extrenity.—The humerus (Pl. VI. figs. 9-11, where that of Majaqueus 
equinoctialis 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 promi- 
nent and triangular, 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 re- 
curved; 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 capitellum 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 brachialis anticus 
is deep and oval. 
Above the external condyle there is a very strong, forwardly-directed epicon- 
dylar process, from which arises the more superficial of the bellies of the extensor 
(Z00L. CHALL. EXP.—PART xt.—1882.) L7 
