28 THE VOYAGE OF H.M.S. CHALLENGER, 
the tendinous band to the ulnar fascia—which represents the morphological termination of 
the tensor patagw brevis—arises in the Albatrosses nearer the middle of the fibrous 
tissue lying between the two ossicles. As in the Cistrelateze and Puftinez, the tendon 
of origin of the superficial part of the extensor metacarpi (e.m.) is double, and in the 
figure an arrow is introduced between them to show this double nature. The proximal 
and smaller of these two ossicles is developed, as before, in the more superficial of these 
twin tendons. The larger of the two ossicles is somewhat different in shape in the 
Albatrosses and Petrels, being more hammer-shaped in the latter group.! 
The presence of these peculiar wing-ossicles is thus confined to the Diomedeine, and 
to the genera Mojaqueus, Puffinus, Bulweria, and Gistrelata (in which last there is only 
one), and, according to Reinhardt (s.c., p. 183) Adamastor, of the Procellariine. In 
the genus Fregata there is a similar small bony nodule developed at the point where, as 
in the Petrels, the inner part of the tensor patagw longus tendon meets the tendon of 
the superficial belly of the extensor metacarpi, and from it radiate out tendinous fibres 
to the patagial margin. I have observed similar ossicles, developed at points of inter- 
mittent straining, in several other birds, as Larus argentatus and glaucus, Fratercula 
arctica, and Merops. 
These bones must be considered to be of the nature of sesamoids, which, as is well 
known, are often developed in the tendons of muscles at the points of greatest strain. 
Their occurrence therefore in different groups of birds is by no means a proof of any 
genetic connection between such, 
Biceps—tThis muscle, in all Tubinares, is remarkable for its excessive reduction, the 
muscular bellies being small and short, and the tendon of insertion excessively narrow and 
thin (vide Pl. IV. figs. 1, 4, and 6, 6). 
It is best developed perhaps in the Diomedeinz, where as usual it arises by two 
heads, a coracoid and humeral (vide Pl. II. fig. 5, ¢., h.), both, however, being largely 
tendinous, and soon uniting. From the coracoid head is given off a very narrow slip, 
chiefly tendinous with a few fleshy fibres only, which runs down in the patagium, and 
joms the margin of the patagium formed by the tensor patagw longus close to the 
elbow (PI. III. fig. 5, and Pl. IV. fig. 3, b.s.). 
In the Oceanitidee the biceps muscle is very slender. It has the two usual heads 
of origin, the tendons of these being often closely united together by fibrous tissue, 
and ending in a small short, common belly. This apparently gives off no “ biceps-slip” 
at all.? 
1 Cf. also the figures of these ossicles given by Reinhardt (s.c., p. 128). 
2 The dissection of these parts in this group of birds is attended with considerable difficulty, partly owing to the 
smallness of the various parts involved, partly to the great accumulations of fat round the tissues, making the true 
nature of these very difficult to determine in spirit specimens. It would be very desirable to dissect out these parts in 
fresh specimens, 
