28 THE VOYAGE OF H.M.S. CHALLENGER. 



the tendinous band to the ulnar fascia — which represents the morphological termination of 

 the tensor patagii brevis — arises in the Albatrosses nearer the middle of the fibrous 

 tissue lying between the two ossicles. As in the (Estrelateae and Puffinese, 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. 1 



The presence of these peculiar wing-ossicles is thus confined to the Dioniedeinse, and 

 to the genera Majaqueus, Puffinus, Buhveria, and CEstrelata (in which last there is only 

 one), and, according to Reinhardt (s.c, p. 133) Adamastor, of the Procellariinas. 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 patagii 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. — This 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, b). 



It is best developed perhaps in the Diomedeinse, where as usual it arises by two 

 heads, a coracoid and humeral (vide PI. III. fig. 5, c, 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 

 joins the margin of the patagium formed by the tensor patagii longus close to the 

 elbow (PL III. fig. 5, and PL IV. fig. 3, b.s.). ' 



In the Oceanitidad 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. 2 



1 Of. 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. 



