C. J. Sundevall on the Wings of Birds. 443 



We pass on now to a short description of the muscles in 

 some isolated forms which are the most aberrant that I know 

 of. 



Cypselus has appeared to me to show a single agreement 

 with the Song-birds, namely, in the extremely small extensor 

 carpi radialis hrevis. It further resembles Hirtmdo only in 

 having 2ifexor digitorum sublimis, which is nearly as large as 

 the flexor carpi ulnaris and commences from the condylus 

 internus ; but these muscles are not placed as in the Swallow 

 and the Oscines generally, but as in the non-Song-birds, the 

 former being situated quite on the radial side of the latter, 

 separated therefrom by the continuation of the fascia tendinea, 

 which is distinctly of equal breadth. Moreover the bellies 

 of the muscles are not rounded, but rectilinear, and continue 

 fleshy nearly to the carpus. The non-Song-bird type is there- 

 fore completely retained, but in other respects the course of 

 the muscles is very different. 



The extensor carpi radialis longus is unusually broad, and 

 commences above at ^ the humerus ; the extensor digitorum 

 communis is also unusually broad at the root ; the extensor 

 indicis small, otherwise as usual; the anconeus parvus as usual, 

 to \ ; the flexor digitorum profundus inserted on the condylus 

 internus humeri ! and nearly as large as the extensor carpi 

 radialis longus ; course of the sinews as usual. The flexor 

 carpi radialis commences near the base of the ulna. The 

 pronatores are very strong, the upper one something more 

 than I, the lower one rather over |, contracted at the apex, 

 not dilated ! The supinator to ^. 



Picus agrees in most respects with the Song-birds, so that 

 we need only indicate the differences, all of which show an 

 approximation to the non-Song-birds. They are as fol- 

 lows : — 



a. The pronator inferior has an unusual structure, which I 

 have seen elsewhere only in Pernis apivorus; for it is attached 

 to the membrana interossea and to the ulna just as much as 

 to the radius (in one specimen of Picus major it was only 

 attached to the ulna ; but in two others, and in P. martins, 

 was as just mentioned) ; it extends somewhat beyond ^ of the 



