38 
know whether it is there associated with a special development of the 
scapular triceps. Mivart and Murie note that in Dasyprocta (and in 
Rabbit, Hare, and Guinea-pig)* the usual three heads are present with 
the usual origin and insertions. The scapular head is large and arises 
partly from fascia over infraspinatus. 
In Talpa}+ the triceps is large and tricipital. The scapular head 
arises from the glenoid end of axillary border or from three-fifths of 
the length of the infraspinous fossa. In the Hrinaceidae the triceps 
is ‘‘ enormous in comparison with the size of the animal.”’; It arises 
by a scapular and two humeral heads. 
Among the Carnivora a post-scapular spinous ridge is figured by 
Giebel in Ursus arctos,$ while Windle|| in the same genus describes 
the scapular triceps as arising from the “ whole of the axillary border.” 
Cuvier and Laurillard figure such a form of the scapular triceps in Ursus 
Americanus ;{ and in Ursus meles** they likewise figure a double scapular 
triceps, the hinder portion being long and slender (noted as a fifth 
extensor), and arising close to the vertebral end of the “ axillary 
border” (and doubtless from the dorsal portion of such a tricipital 
ridge or post-scapular spine as is present in U7sis arctos.) This origin 
overlaps dorsally the origin of the teres major. 
In some cases where such a posterior, or rather post-axial, sector of 
the scapular triceps is present it appears to be more or less closely 
associated with the dorso-epitrochlearis (Cuvier and Laurillard’s 
fourth extensor; Wenzel Gruber’s anconeus V.). Such a condition 
of partial union is noted by Galton as present in Orycteropus capensis} +, 
and in Dasypus sexcinctus.¢ t 
On the general morphology of the extensor mass in the arm in 
Mammalia c.f. memoir by Wenzel Gruber.$§ 
Mf. anconeus externus seu quartus, seu epicondylo-anconeus 
(W. Gruber) (figs. 8, 9, and 17 az.e.). This is a comparatively 
large muscle, somewhat rhomboidal in form, and arising from 
the back of the ectocondylar ridge of the humerus in its promi- 
nent lower third. Its fibres are directed backwards and distally 
towards the ulna, to be inserted into the base of the olecranon 
and the proximal half af the postaxial border of the shaft of the 
ulna. 
Its attachment to the ulna. is crossed by the belly of the M. 
extensor indicis et medii digiti, which runs along the shaft of 
the bone. 
The proximal border is parallel with the lateral border of the 
humeral triceps, superficially with the outer head, but deeply 
it is in apposition with the short fibres of the inner head, from 
which indeed it is not absolutely separable by any very marked 
segmentation cleft. 
Its distal border is parallel and in apposition with the ulnar 
border of the extensor carpi ulnaris (fig. 9, e.c.2.). 
*xl., page 400. + xi., page 215. "(+ vili., page 395. §xviii., Pl., 72, fig. 5. 
| Ixvi., page 83. WI vi., Pl. 85-6.’ ** vi., Pl. 102. tt xv., page 578. Tf xiv., 
page 539. S$ lviii., page 8, et seq. 
