320 PROF. HUXLEY ON ARCTOCEBUS CALABARENSIS. [June 28, 
The sole of the foot is formed behind, as usual, by the tuberosity 
of the caleaneum, and is bare ; in front, where the hallucal and di- 
gital divisions of the foot diverge, there is a callous oval projection 
(fig. 2, C, a) supported by a large sesamoid bone. The skin is bare 
on this projection ; but between it and the ball of the heel is a narrow 
hairy band. 
Dr. Smith does not mention the circumstance ; but, in the hand of 
the present specimen, the two distal free phalanges of the third 
digit are not parallel with those of the fourth and fifth digits, but - 
are directed obliquely inwards (fig. 2, A). 
With Dr. Smith, I find only two phalanges in the index finger (the 
second being very short and slender), and no trace of any nail, the 
only marking on the exterior of the digit being that produced by the 
projection of the end of the metacarpal bone. 
The proximal phalanx of the index finger is 0°15 inch long; the 
distal rather less than 0-1 inch. 
Thus far the differences between my specimen and that described 
by Dr. Smith are of no moment; but on passing to the dentition I 
find, with a complete general correspondence, a solitary discrepancy 
which I cannot account for, 
Dr. Smith says of the upper incisors :—‘‘ Two together (in pairs), 
with intermediate edentulous space ; first incisor the smallest; the 
second nearly twice as large as the first.’ 
In the specimen under description, on the other hand, the upper 
incisors are strictly equal in size; and the proportions of the two 
teeth noted by Dr. Smith are the more remarkable, as they do not 
obtain in any other Lemurs. When, as in Nycticebus and Tarsius, the 
upper incisors are unequal, it is the outer which is the smaller. 
In the face of the resemblances of size, proportion, pelage, and 
sex between the two specimens of Angwantibo, it is difficult to 
admit that this singular difference can have more significance than 
an individual variation. However this may be, the characters of the 
teeth of the Angwdntibo are so well shown in the present specimen 
that I shall describe its dentition at some length, and compare it 
with that of the other Lemurs. 
The series of teeth belonging to the adult dentition is complete 
(except the right outer incisor, which is broken off at the root), and 
the crowns are not at all worn. The total number of the teeth, as 
in the majority of the Lemurs, is 36; and the dental formula is— 
- 2-2 = = = 
a = e.; pm. = m. — 
In the upper jaw (A, C, fig. 3) the incisors (¢) are set in a nearly 
straight transverse line, at the outer ends of which are the canines 
(c). The distance from the outer edge of one canine to that of the 
other is 0°4 in. The inner edges of the grinders (1-6) are also arranged 
in straight lines ; the distance of the right and left series, anteriorly, 
is 0°3 inch, posteriorly, 0-4; while the length of the series is 0°7 inch. 
The five hinder grinders are close together ; while the first premolar 
is separated from the second by a slight interval—less, however, than 
that which separates the first premolar from the canine. 
