39 
According to Cunningham,* this muscle varies greatly in the dif- 
ferent members of the order Marsupialia, in which, however, it is very 
generally present. 
In Thylacinus he describes it as hardly existent, while in Phascogale, 
and especially in Cuscus, it is largely developed. 
In Myrmecobius fasciatus Leche+ describes it as especially strongly 
developed. From his figure it does not appear to be proportionately 
so largely developed as it is in Notoryctes. 
In Phalangista vulpinat it extends over the upper two-fifths of the 
outer border of the ulna as a very considerable muscle. 
In Echidna Westling$ notes the anconeus externus (“ quartus”’) as 
arising from the dorsal aspect of the ectocondyle, and inserted into a 
depression on the external face of ulna (olecranon and shaft), extend- 
ing distally as far as the extensores digit. com. and carpi ulnaris. 
In Ornithorhynchus a well-developed anconeus externus is also present. 
According to St. John Brooks,|| it arises in common with the extensor 
carpi ulnaris from the external condyle, and is inserted into the upper 
third of the ulnar shaft. (This author? regards the anconeus externus 
of the vertebrate forelimb as morphologically related more nearly to 
the extensor carpi ulnaris than to the inner head of the triceps, and as 
constituting along wth the former the ulnar sector of the superficial 
layer of the extensor mass in the antibrachium. Its “tendency to 
unite with the triceps’’ he regards as a secondary, and not as a primary, 
characteristic. The condition in Notoryctes would agree equally well 
with either view of the affinities of the muscle, but the evidence from 
mere topographical relationship is of little value.) 
In Chlamydophorus** the anconeus externus is comparatively small, 
_and it is overlapped by the humeral triceps, and in Tatusia the condi- 
tion issimilar.t}+ Humphry7¥+ notes that in Cyclothuwrus (Myrmecophaga) 
didactyla it extends down nearly the whole length of the outer surface 
of the ulna between the extensor carpi ulnaris on its outer side, and 
the flexores digiform and carpi ulnaris internally, these three muscles 
(four ?) forming an almost continuous sheet. In Manis, too, the same 
author describes the anconeus externus as large. 
Amongst the Insectivora Dobson} i} notes the presence of the anconeus 
externus only in the Talpide. In Talpa Europea the muscle, according 
to Freeman,§§& consists of two parts, a posterior rounded fusiform fas¢i- 
culus arising from tip of the styliform external condyle and inserted 
into the outer projection of the olecranon. The anterior portion is 
thin and fan-shaped, arises in common with the preceding, and “ be- 
coming aponeurotic as it passes over the extensor muscles of the fore- 
arm, is inserted into the prominent crest of the ulna.” 
Cuvier and Laurillard figure a well-developed anconeus externus in 
the Hedgehog as well as in the Mole. |||| 
The anconeus externus appears to be but slightly developed (gener- 
ally absent ?) amongst Rodents. However, Cuvier and Laurillard figure 
the muscle in Sciwrus (pl. 204) and in Arctomys (pl. 207), where it is 
indeed rather well marked. 
*iv., page 12. +xxvi., page 806. {xxxvi., page 122. §lxii., page 20. 
|i., page 9. [i., pages land 13. ** xxvii., page 248. Tt xxi., page 39. 
££ Quoted by Leche, xxvi., page 806. §§xi., page 215. ||| vi., Pl. 80, fig. 
Bw, and Pi. 75, fig. 1 u. 
