50 MESSRS. MURIE AND MIVART ON THE 
palm. These arise side by side from the ligaments and deep carpal fascia close to the 
proximal ends of the two median metacarpals. The one is inserted into the ulnar side 
of the second metacarpal; the other also by a short tendon into the fascia on the radial 
side of the fifth metacarpal, its distal end. The distribution of the so-called dorsal 
interosseal slips almost agrees with the condition described in Tarsius. Those of the 
Grand Galago are drawn in Pl. II. fig. 3, and Pl. IV. fig. 13,1. 1.1.1; and in the 
enlarged view, Pl. IV. fig. 15, the two interossei superficiales are marked Is. Is. 
Burmeister! describes the interossei as consisting of internal and external ones. 
According to him the internal interossei? are four in number, and spring deeply 
between the metacarpals. The first attaches itself to the ulnar side of the index. The 
second divides into parts, going respectively to the ulnar side of the third digit, and to 
the radial side of the fourth digit. The third to the ulnar side of the fourth digit. The 
fourth is inserted to the radial side of the fifth digit. 
The external interossei, as he states*, spring from the dorsal side of the metacarpals ; 
they also are four in number. The first (abductor indicis) is inserted into the radial 
side of the first phalanx of the index. The second divides, and goes to the adjacent 
sides of the second and third digits. The third goes to the adjacent sides of the third 
and fourth digits. The fourth is inserted into the adjacent sides of the fourth and fifth 
fingers. 
In Cheiromys, in addition to the ordinary interossei, we find a small more super- 
ficial layer which arises in the deep fascia of the carpus, and divides into two small 
bellies. One of these is inserted into the ulnar side of the index digit, the other into 
the radial side of the fifth digit. The ordinary interossei form a considerable body of 
muscle on the dorsum of the fourth and fifth metacarpals. 
3. Muscles of the Trunk. 
a. Ventral Region (Thoracic and Abdominal Parictes). 
SupracostaL Muscies.—On each side of the thorax, between the long insertion of the 
scaleni and origin of the pectorals, but superficial to the intercostal muscles, there are 
two small but very distinct muscles. These appear to be the variety so named by Mr. 
John Wood in his paper on “ Additional Varieties in Human Myology,” read before the 
Royal Society in June 1865 ‘—and also to two unnamed extrapectoral muscular bundles 
described and figured by Van Campen in the Potto’ (Perodicticus) as early as 1859. 
We ourselves have observed equivalent muscles (though unpublished) in several 
Mammals, e. g. the Common Zebra, Brown Bear. Giraffe, &c. 
But Cuvier, in those plates which form his posthumous ‘ Recueil de Myologie’ (the 
' Loe. cit. p. 66. * Loe. cit. tab. 5. fig. 5, no. 46. 3 Loc. cit. tab. 5. fig. 3, nos. 44 & 48. 
* P. 381, and reprint from the Proceedings of the Royal Society, 15 June, 1865, p. 3, fig. 1, d. 
° Loe. cit. p. 27, pl. 2. fig. 10. 
