436 C. J. Sundevall on the Wings of Birds. 
radialis longus, and thus clothes the whole outer side of the 
hone. 
In other respects the muscles are disposed in the follow¬ 
ing manner (the conditions noticed in parentheses are 
certainly general in the Song-birds, hut not characteristic of 
them):— 
The extensor carpi radialis longus is the largest of all, only 
§ 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 § 
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 ulnae, 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 J 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, &e. 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 below towards the ligamentum carpi, often 
