1889.] ANATOMY OF POLYBOROIDES. 79 
I find an identical arrangement of these tendons in Circus maurus, 
and they appear to be exactly the same (judging from a MS. sketch 
by Forbes) in Spizaetus occipitalis and Aquila imperialis. In 
Milvago chimachima and in Haliaetus albicilla and Astur approz- 
imans (Forbes, MS.) the tendon is single, but there is a trace of the 
second tendon in a short fibrous slip which, arising from near the 
Fig. 1. 
Migs 
Tensores patagii and other muscles of Polyboroides typicus. 
t.p.l, tensor patagii longus; ¢.p.b7, tensor patagii brevis; Anc, anconeus; D, 
deltoid. 
(The dotted parts represent tendons in this and the following figure.) 
insertion on to the forearm of the ¢ensor patagii tendon, ends upon 
the patagium. ‘This tendinous band may, however, perhaps be 
considered as the equivalent of the tendon which in other Accipitres 
(v. infra) unites the tendon of the tensor patagii longus with that 
of the tensor patagii brevis at the insertion of the latter on to the 
forearm. 
In Gypohieraxr* the tensor patagii brevis rerembles that of Poly- 
Loroides except that the outermost of the two tendons near to the 
* Fiirbringer, Untersuchungen z. Morph, und Syst. d. Végel, pl. xxii. fig. 9. 
