535) 
In Koala* Young describes the muscle as arising from the whole of 
the outer surface of the shaft of the humerus, and inserted in common 
with the gleno-ulnar moiety of the biceps 
In Echidna} the muscle is small and delicate, arising from the outer 
side of the shaft of the humerus, and closely embraced externally by 
supinator longus. . 
In Ornithohynchus also it is said to be intimately related to the supi- 
nator longus (v. infra, p. 42), and here it is innervated both by the 
N. medianus and M. radialis.¢ It is inserted into the radius. 
In Chlamydophorus$ the muscle is large and, as in Notoryctes, is 
separated from the hiceps by the deltoid tuberosity. Below, however, 
they are connected and inserted in company. 
The insertion is radio-ulnar in Bradypus tridactylus,$ and there is a 
radial slip also in Oryctevopus,|| where also it receives a slip from the 
biceps. 
In Talpa{i its origin is from the upper part of the outer surface of 
the humerus and from the hook-like process on the outer tuberosity. 
It is ulnar in insertion. 
In Erinaceus** and Gymnuwrat +t it is inserted into the radius. 
It is altogether absent in Chrysochlorist ¢. 
In several Rodents$$ (Dasyprocta, Lens, Cuniculus, &c.) the muscle is 
divided into two distinct parts, and is ulnar in its insertion. 
M. triceps extensor antibrachii (figs. 1, 4, 5, 6, 7, and 8, ¢r., 
s.tr., i.h.tr., and o.tr.) forms a relatively large muscular mass 
extending dorsad of the region of the axilla. Its origins are 
scapular and humeral, and the humeral origin is partially separ- 
ated into ‘“‘outer” and “inner” heads. 
The scapular origin (figs. 6-8, s.é7.) is very extensive. It arises 
from the whole of the actual posterior border of the scapula from 
the glenoid origin to the recurved posterior angle of the vertebral 
border. It also arises from the whole length of the secondary or 
post-scapular spine of the scapula, and from the whole of the 
surtace intervening between this and the posterior margin of the 
bone. 
Part of this origin is crossed dorsally by the fibres of the 
spino-deltoid arising from the meso-scapular spine. . 
The humeral fibres of the muscle arise from the whole of the 
morphologically dorsal aspect of the humerus. The “ outer” 
head (fig. 8, 0.¢7.) arises from the proximal part of this surface of 
the shaft, extending outwards as far as the upper end of the 
ectocondylar ridge, where, and above which, its outer marginal 
fibres are parallel with and closely applied to the outer margin 
of the brachialis anticus. Lower down the outer margin is in 
superficial apposition (hehind the ectocondylar ridge) with the 
proximal margin of the anconeus externus. The highest part of 
*Ixxil., page 227. . | xxxix., page 386. .}xxvi., page 804. § xxvii., 
page 247. ||xv., page 576. ‘I xi., page 215. **xxvi., page 804. tt viii., 
page 395. tfxxvi., page 804. S$ xl., page 399. 
