272 ZAGLOSSUS. 



three divisions. The cnjmt 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 lalissimus dorsi, previously noticed, are in the 

 Echidna from nearer the vertebral edge, since their origin is slightly dorsal to 

 tliat of the caput lonytim. 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 hrachioradialis 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 tliat runs over the distal head 

 of the radius and inserts upon the dorsal surface of the combined radiate 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 



