REPORT ON THE ANATOMY OF THE PETRELS. 27 



found iu the tendon of the superficial part of the extensor where it arises from the 

 humerus. 



In Majaqueus (PI. IV. fig. 7), Bulweria, and Puffinus the tensor patagii brcvis 

 (t.p.b.) tendon is not fused with the much broader and stronger tensor patagii longus, 

 but is a distinct, very slight, slip, lying between this and the humerus. 



At the elbow it joins the superficial ossicle (a), developed at the junction of the 

 tensor patagii with the extensor tendons. In Pvjffinus (brevicauda and obscurus) 

 this thin tensor patagii brevis is split below into two slips, one joining the deeper of 

 the twin tendons of origin of the superficial extensor, whilst the other is inserted on the 

 supracondylar process. The ossicle is larger than the corresponding one of OEstrelata, and 

 of somewhat smaller form ; from it spring both tendinous fibres for the patagial tendon, 

 and fleshy fibres for the superficial belly of the 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. Proximad of this larger ossicle is a smaller, more circular, one (a'), which 

 is developed in the more superficial 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 IV. fig. 5. 



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 

 metacarpi radialis longior (e.m.), from which it is continued onwards to the ulnar fascia 

 by two well-defined bands. Between the most wristward of these and the marginal 

 tendon of the patagium 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 Diomedeinse the arrangement (PI. IV. fig. 3) more resembles that of the 

 Puffineas, 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 (b.s.). 



The relations of the ossicles are very nearly as in Majaqueus (vide the figures), but 



