MR. ST. GEORGE M1VART ON THE SKELETON OE THE PRIMATES. 
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It is rather convex outwards in the Nycticebinge. Sometimes there is a sigmoid 
vertical curvature, as in Nyctipithecus, Hapale, Indris, Galago, and Tarsius. 
The ridge for the popliteus is very rarely distinguishable in any Anthropoidea except 
Man. In the Lemuroidea there is generally a marked vertical ridge at the upper part 
of the posterior surface of the tibia. This appears to attain its maximum in Arctocebus 
and Perodicticus. 
The ridge for the interosseus membrane, which is so strongly marked in Man, is not 
distinct in the Simiinae or higher Cebidee, but it is more so in other Simiidas and Cebidse, 
and in Hapale. Sometimes in Lemur it is strongly marked, but not in any of the 
Nycticebinge. 
The malleolus is generally well developed, but sometimes, as in the Prang, very 
short. It is long in Cynocephalus, Lemur, Galago, and Cheiromys, and in some 
(the Nycticebinae) it is much pointed, incurved, and antero-posteriorly compressed, with 
its articular surface very convex. Moreover, it seems rather to spring from the front 
than from the inner side of the shaft of the tibia, as is very well seen in Perodicticus. 
The articular surface of the malleolus is sometimes nearly at right angles with the in- 
ferior surface of the shaft of the tibia, as in Man, the Chimpanzee, and the lower An- 
thropoidea ; sometimes it forms an obtuse angle with that surface, as in the Gorilla, and 
still more in the Orang. 
A groove for the tendon of the tibialis posticus marks the back of the malleolus ; this 
attains its maximum of enclosure and relative depth in the Nycticebinge, where the por- 
tion of bone which separates it from the (also strongly, though less marked) groove for 
the flexor longus hallucis has the appearance of a prominent process. 
The distal articular surface of the shaft of the tibia is horizontal transversely in Man, 
Ateles, and Lagothrix. In the Simiidge and lower Cebidge the outer portion rises so that 
the articular surface slopes upwards and peronead ; and this is still more the case in the 
Lemuroidea. 
As regards the anterior and posterior margins of this articular surface, they descend 
in general about equally ; but in some Cebidge ( e . g . Callithrix) and Lemuroidea ( e . g. 
Lemur, Galago, Tarsius) the anterior border descends a little further than does the pos- 
terior one. On the other hand, the posterior margin descends considerably more than 
does the anterior one in Man, and might be supposed to do so in the Nycticebinge, on 
account of the projection in the latter of the process of bone separating the grooves for 
the flexor tendons. 
This inferior articular surface is generally subquadrate with a median antero-posteriorly 
directed prominence. In the Lemuroidea it tends to approach a triangular form, and 
the prominence in the Nycticebinge [e.g. Loris) becomes very large. 
The pit for the insertion of the tendon of the semi-membranosus is generally distinct, 
but often slight, as generally in Lemuroidea, though in Arctocebus it is very strongly 
marked. It is only in Indris that I have observed a tubercle projecting downwards 
immediately beneath it. 
