272 ZAGLOSSUS. 
three divisions. The caput longum has origin by a short stout tendon just 
dorsal to the glenoid cavity of the scapula, at the ventral end of a small ridge. 
In the Echidna this origin is much more extensive, and is represented as con- 
tinuing dorsally almost to the vertebral edge of the scapula. Also the deltoid 
and the small branch of the latissimus dorsi, previously noticed, are in the 
Echidna from nearer the vertebral edge, since their origin is slightly dorsal to 
that of the caput longum. The insertion of this muscle is as usual into the tip 
of the olecranon. The caput laterale arises by a stout tendon from the lateral 
face of the humerus at nearly the end of its proximal third. It inserts at the 
external corner of the olecranon, and is fused distally with the caput mediale. 
This last covers the entire posterior aspect of the humerus, from just below the 
head, to the deltoid ridge and inserts into the middle and medial borders of 
the olecranon beneath the caput longum. 
The brachialis in the Proechidna is almost inseparable from the brachio- 
radialis, along the medial side of which it is so closely applied as to be with 
difficulty separated. Its origin is just lateral to the anterior edge of the humerus 
at about the end of its proximal third. It passes to the ulna, on whose medial 
side it is inserted by a thin tendinous sheet just anterior to the sigmoid notch. 
The anconeus (Plate 1, fig. 3, an) is a well-defined band some 30 mm. long 
that arises at the external border of the posterior distal tubercle of the humerus 
and passes anteriorly to the olecranon of the ulna where it inserts just posterior 
to the caput mediale of the triceps. 
The brachioradialis is similar to that of the Echidna. It arises on the 
external side of the humerus, distal to the tendon of origin of the caput laterale 
of the triceps, and occupies nearly the middle third of the humerus. It passes 
as a thin sheet to a partly tendinous insertion along the medioventral border 
of the radius for some 25 mm. distal to the sigmoid notch. Its internal surface 
is very closely connected with the brachialis, which, however, is of about half 
the extent of the brachioradialis along the line of insertion, 
The extensor carpi radialis longus (Plate 1, fig. 2, erl) is a narrow muscle, 
somewhat triangular in section, that arises from the lateral supracondyloid 
ridge of the humerus, just distal to the brachioradialis. Slightly beyond the 
middle of the radius it passes into a flat tendon that runs over the distal head 
of the radius and inserts upon the dorsal surface of the combined radiale and 
intermedium (‘‘scapholunar bone’’). 
The extensor carpi radialis brevis (Plate 1, fig..2, erb) is of nearly four times ~ 
the bulk of the longus and arises just external to it from the supracondyloid 
