392 OX THE PETRELS COLLECTED DURING 



extensor (e.m.) ; from it also, or from the fibres of the last muscle, passes 

 off a thin tendinous fasciculus (f.) to the ulnar fascia. Proxirnad of this 

 larger ossicle is a smaller, more circular, one (a 1 ), which is developed in 

 the more supsrficial of the twin tendons already described a little beyond 

 its origin, where it plays over the supracondylar process. This second 

 ossicle is very small in Bulweria. 



In the genera Pagodroma, Daption, Fulmarus, Thalassceca, Aeipetes, 

 and Ossifraga, no bony nodules are developed, but the arrangement of 

 these tendons at the elbow becomes very complicated. Their arrangement 

 in Ossifraga, with which the others are almost identical, is represented 

 in Plate XVIII. fig. 2. 



The tensor patagii longus (t.p.l.} tendon divides near the elbow into 

 two parts, one continuing as the marginal patagial tendon, provided 

 with the usual cushion of elastic tissue opposite the bend of the 

 arm, the other receiving the much thinner tensor patagii brevis (t.p.b.}. 

 The united tendon so formed becomes somewhat diffused distally, and 

 more or less fused with the superficial tendon of origin of the extensor 

 melacarpi radialis longior (e.m.\ from which it is continued onwards to 

 the ulnar fascia by two well-defined bands. Between the most wrist- 

 ward of these and the marginal tendon of the patagi urn there is developed 

 a narrow vinculum. 



In addition to this the main tendon of the tensor patagii, which has a 

 clear, well-defined edge on its humeral side, where it crosses the extensor 

 muscle, sends a small special slip of tendon (t.p .) to the deeper of the 

 two bellies of that muscle. 



In the Diornedeinse the arrangement (PI. XIX. fig. 4) more resembles 

 that of the Puffinese, as here also two ossicles are developed with nearly 

 the same relationships to their surroundings as in that group. The tensor 

 patagii brevis (t.p.b.)is separate from the tensor patagii longus (t.p.l.) till 

 near the elbow, the marginal tendon of the latter muscle having received, 

 a little before, the very long and thin tendinous biceps slip (6.5.). 



The relations of the ossicles are very nearly as in Majaqueus (vide the 

 ^ool. Chall. figures), but the tendinous band to the ulnar fascia which represents 

 Exp. Tol.^iv. 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 Puffineae, 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 de- 

 veloped, as before, in the more superficial of these twin tendons. The 

 larger of the two ossicles is somewhat different in shape in the Alba- 

 trosses and Petrels, being more hammer-shaped in the latter group *. 



* Cf. also the figures of these ossicles given by Eeinhardt (*. c., p. 128). 



