REPORT ON THE ANATOMY OF THE PETRELS. 25 
anterior end of the muscle on the breast close to the symphysis furcule, and goes to 
the skin of the lower and anterior aspect of the neck. 
Pectoralis secundus.—This muscle is also well developed, but though broad is 
usually short, extending for not more than one-third, one-half, or sometimes two-thirds 
the length of the sternum. In Pelecanoides, however, it is much longer, extending to 
nearly the end of that bone, and in Procellaria, Garrodia, Fregetta, and Pelagodroma 
its extent is nearly as large, in which cases it extends beyond the posterior margin of 
the deep layer of the first pectoral. 
It arises from the antero-superior part of the carina sterni, and from the body of the 
bone external to that, from the greater part of the coraco-fureular membrane below the 
pectoralis tertius, from the symphysis furcule, and from a greater or less extent of 
the antero-inferior border of the coracoid bone. Its insertion is by the usual tendon on 
the superior aspect of the humerus, behind the much smaller tendon of the third pectoral. 
In the Albatrosses the pectoralis secundus is unusually short, and broken up into 
four quite separate parts, which unite before passing the shoulder-pulley. This arrange- 
ment is clearly shown in fig. 2 of Plate III. representing the muscle in Diomedea brachyura. 
In the other Petrels, the muscle is much more homogeneous, and only separable by 
dissection into its various component parts. 
Pectoralis tertius.—This muscle (Pl. II. fig. 2, p. 3) is always well developed in the 
Tubinares, in the form of a broad, thin band, more or less parallel with the coracoid, 
occupying the superior half of the broad space between that bone and the fureula, its 
fibres arising chiefly from the strong membrane between these bones, sometimes with 
additions from the anterior margin of the coracoid, or from the body of the sternum 
close to the middle line. 
Tensor patagi brevis and longus.—These muscles have always a common, rather thin 
and flat fleshy belly, arising from the extreme upper end of the clavicle, and receiving, in 
addition, special small slips from the surface of the great pectoral. From this fleshy 
belly spring two tendons, of which one always forms the marginal patagial tendon, and 
must therefore be considered as the tensor patagi longus. Both the tendons are con- 
nected, close to their origin, by fibrous slips to the humeral crest, from which indeed 
they might be said to arise, receiving then the main muscular belly. The connection of 
the marginal tendon with the humerus is always provided with a small tract of strong 
elastic tissue (wde Pl. IV. fig. 7, t.p.l’.), and another such tract of longer extent is found 
on its course opposite the bend of the elbow (PI. IV. figs. 3 and 7). 
In other respects the development and distribution of these tendons differs much in 
different groups of genera, and their arrangement will therefore be here considered 
seriatim. 
It is in the Oceanitide that the disposition of the tendon of the tensor patagii 
brevis (t.p.b.) is simplest, it here, in all the four genera, passing straight downwards 
(ZOOL, CHALL. EXP.—PART XI.—1882.) L4 
