444 DR. J. MURIE ON THE ANATOMY OF THE WALRUS. 
The single-bellied biceps (woodcut, fig. 4, B) is remarkably weak. 
Of the brachialis anticus it cannot be said to be a double-bellied muscle (woodcut, 
fig. 4, B.a), though its heads, two in number, embrace the humerus on either side of 
the prominent deltoid eminence. The innermost portion runs up quite to the root of 
the radial tuberosity, whereas the outer origin arises closely approximated with and 
deeper than the supinator longus. 
Superficial view, dorsal aspect, of left pectoral limb. 
O.h. Cephalo-humeral. Tz’. First portion of trapezius, 
its insertion. Zz*. Second portion of trapezius. D*. 
Deltoid, main or first portion. Jsp. Infraspinatus. 
D.ep, Dep*. Dorso-epitrochlear. 1, T°. Triceps, 
first and second bellies. -A.e. Anconeus externus. 
P.mi. Peetoralis minor, its insertion turned forwards. 
B.a. Brachialis anticus. S./. Supinator longus. E.c. 
rl. § b. Extensor carpi radialis longior and brevior. 
E.p.i.p.&c. Extensor primi internodii pollicis. #.c.(7. 
Extensor communis digitorum. H.me.d. Extensor 
medii digiti. H.m.d. Extensor minimi digiti. Meu. 
Estensor carpi ulnaris. Z. p ji, Extensor pollicis et 
indicis. J-V. Digits. 
‘The supinator longus (woodcut, fig. 3, S./), single and laterally compressed, arises from 
the lower part of the deltoid ridge and the shaft of the humerus below it. Its tendon 
of insertion is long, but not very broad, and proceeds to the styloid process. 
Arising from the outer condyle and without the tendency to a double head of origin 
exhibited in the Sea-lion, the supinator brevis in the Sea-horse, with a thickish fleshy 
belly, is inserted on the outer edge of the shaft of the radius, as far as the prominence 
at the lower end of the shaft. 
