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



radialis longus, and thus clothes the whole outer side of the 

 bone. 



In other respects the muscles are disposed in the follow- 

 ing manner (the conditions noticed in parentheses are 

 certainly general in the Song-birds, but not characteristic of 

 them) : — 



The extensor carpi radialis longus is the largest of all, only 

 I fleshy, undivided, with a strong flattened sinew; the ex- 

 tensor brevis is extremely small or rudimentary ; the extensor 

 carpi ulnaris has a long sinew, which commences at about f 

 the length of the ulna, and terminates upon a small tubercle 

 on the ulnar edge at the base of the third (anchylosed) 

 OS metacarpi. (The extensor digitorum communis is of ordinary 

 form. The extensor indicis, from the basis radii, without 

 accessory muscles in the region of the carpus.) The posterior 

 flexors have already been described. (The flexor digitorum 

 profundus starts from the basis ulnce, the sinew is strong and 

 long; the flexor carpi radialis from \ of the ulna.) The 

 pronatores coalesce nearly to a single muscle, which, however, 

 consists of two very distinct bundles, reaching to half the 

 length of the radius. Supinator small, to ^ of the radius. 

 [Humero-ulnaris externus to \ of the ulna.) 



In Hirundo rustica the following deviations occurred : — 

 The flexor digitorum sublimis was but little smaller than the 

 underlying flexor carpi ulnaris, and commenced near it on 

 the condylus humeri ; but the fascia tendinea, as usual, quite 

 membranous, thin, &c. The two pronatores of the same size. 

 All the bellies of the muscles are still shorter than usual, 

 namely that of the extensor carpi radialis longus merely to ? 

 of the cubitus, by which means the outer pits of the cubitus 

 become longer in proportion. In all other respects as 

 in other Song-birds. 



The birds of other Orders which were examined showed 

 the following points of agreement by which they are distin- 

 guished from the Song-birds : — 



a. The fleshy part of the muscles is of more even thickness 

 and is elongated beloAV towards the ligamentum carpi, often 



