ANATOMY OF THE LEMUROIDEA. 75 
In Tarsius' it is as in Lemur catta. 
In Cheiromys Professor Owen? only speaks of a single tibialis anticus muscle and 
tendon answering to that described in L. catta; but in both limbs of our specimen there 
was a double tibialis anticus precisely similar in its conditions to that above described 
in L. varius, xanthomystax, and nigrifrons. 
EXTENSOR LONGUS DIGITORUM °.—This in the right leg of L. catta dissected by us was a 
long, slender and flat muscle, with the edge forwards and overlapped towards its middle 
by the junction of the tibialis anticus with the peroneus longus. It arose from the 
head of the tibia, the interosseous membrane, and the inner side of the fibula, but not 
from its head. It gave origin to four tendons, which went to the four peroneal digits, 
those going to the second and third digits being joined by the corresponding tendons of 
the extensor brevis, while that going to the fourth was joined by the peroneus quarti as 
well as by the corresponding tendon of the extensor brevis, and that going to the fifth 
digit by the peroneus quinti digiti. 
In the left leg of the same animal we observed that a long, prominent tendon on the 
front edge of the muscle was that of almost a distinct muscle by itself, which had a 
very small muscular belly reaching as low down as the whole upper third of the leg. 
Its delicate tendon, when raised from the belly of the true extensor longus digitorum, 
could be traced singly as far as the ankle and in the front of the foot. It bifurcated, 
going to the second and third digits. A slip united that going to the third digit with 
the long extensor tendon of the fourth digit. 
Is this a representative of the extensor indicis of the arm? 
In L. aanthomystax the arrangement is like that of the left leg of L. catta; and in 
L. varius also, except that there are only tendons to the third, fourth, and fifth digits. 
The condition of the specimen of L. nigrifrons which we dissected was not the best 
for accuracy as regards this muscle. The following was what we observed. In the 
partially injured right foot the small tendinous slip noticed in L. varius and L. xantho- 
mystaa was visible; this sent a slip to the second and third digits, as in the two last- 
mentioned species. The extensor brevis also joined the tendons of the extensor 
digitorum. ‘There was, moreover, a minute (broken) tendon going to the fourth digit, 
as also a very long, thin tendon joining the fifth; where this last tendon came from 
was not made out by us. In the left foot (Pl. VI. fig. 27, #./.d) the main tendon splits 
into two, whereof one supplies the second and third digits, the other the fourth and fifth. 
But the fourth also gives off a slip which unites it to the third and second. 
In G. crassicaudatus (Pls. II. & VI. figs. 3 & 25, H.l.d) this muscle gives off three 
tendons, the outermost one going almost exclusively to the fifth digit, the middle one 
bifurcating, one branch going to the fourth digit, the other joining a branch of the inner- 
1 Burmeister, loc. cit. p. 75, tab. 3. fig. 1. no. 24, and tab. 5. figs. 6 & 7. 24. 
2 Op. cit. p. 67, pl. xxv. figs. 1 & 3. no. 24. 
3 See Cuvier, pl. 70. fig. 1, 2, in Lemur varius. 
