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MR. ST. G. MIVART ON THE ANATOMY OF ECHIDNA HYSTRIX. 387 
a bony canal; the ulnar nerve passes beneath the midst of the expanded origin of the 
flexor carpi ulnaris. 
In spite of the peculiar arrangement and position of the bones of the limb in the 
Echidna, the axillary artery lies (as in man) successively on the first rib, part of the 
serratus magnus, the tendon of the subscapularis and that of the teres major. 
Extensor carpi radialis longior (Plate LIL. figs. 1 & 2, £.r.1).—This is a narrow muscle, 
arising, as usual, from the external condyle of the humerus. It becomes tendinous a little 
below the middle of the forearm, and is inserted into the dorsal surface of the distal pro- 
minence of the scapholunar bone. 
The extensor carpi radialis brevior (Plate LII. figs. 1 & 2, E.R.B) also arises from the 
external condyle. It exceeds in size the muscle last described, and becomes tendinous 
rather lower down. Its tendon passes, in common with that of the extensor carpi 
radialis longior, beneath the tendon of the extensor ossis metacarpi pollicis, and is in- 
serted into the metacarpal bone of the third digit. 
The extensor communis digitorum (Plate LII. figs. 1 & 2, s.c) is a wide, flat, somewhat 
laterally compressed muscle, its edge appearing on the surface of the forearm. It has 
two origins—one narrow one from the external condyle, the other, more extensive, from 
the radial side of the posterior margin of the ulna down nearly to the wrist. It is from 
this second origin that the tendon arises, which is very strong, passes downwards through 
a groove on the back of the ulna, lined with synovial membrane and enclosed by a very 
strong ligament, and, dividing into three, is inserted into the index and third and fourth 
digits. 
Extensor minimi digiti (Plate LII. fig. 1, E.M.D).—This is very largely tendinous, and 
arises from the external condyle, and is at its origin closely united with the muscle last 
described and with the extensor carpi ulnaris. It is inserted into the dorsum of the 
fourth digit, after passing through a special groove, on the back of the ulna, lined with 
synovial membrane. 
Extensor carpi ulnaris (Plate LIL. fig. 1, £.u).—This arises from the external condyle 
and from the outer (radial) surface of the olecranon. It becomes tendinous a little above 
the wrist, its tendon passing along a distinct canal on the back of the ulna, lined with 
synovial membrane. Tt is inserted into the outer side of the dorsum of the fifth digit. 
An eztensor indicis appears to be entirely wanting. 
Extensor ossis metacarpi pollicis (Plate LII. figs. 1 & 2, 
delicate muscle, arising from the radial border of the ulna, ! en 
radius, and from the interosseous ligament. A little above the wrist it gives origin to a 
rather strong tendon, which, after erossing over those of the radial extensors, is inserted 
into the metacarpal of the pollex. 
Extensores primi et secundi internodii pollicis.— 
of these muscles. 
The supinator brevis arises, by tendon, 
g.M.p).—This is a thin and 
as high up as the head of the 
I could find no representative of either 
from the external condyle (immediately beneath 
the narrow origin of the extensor communis digitorum), also by muscular fibre from the 
same condyle, beneath the origin of the extensor carpi radialis brevior. It is inserted 
along the outer (radial) margin of the radius for nearly the upper four-fifths of that bone, 
