364 
On the Sesamoids of the Knee-joint 
Hapale jacchus (common marmoset), Jacchus auritus, and two other specimens 
(sp. ?) of Jaccltus, Cebus capuchimis (two specimens), Gehus (sp. ?) (two specimens), 
Lagothrix huutholdtii (two specimens), Pithecia satanas (Black Sahi), Fithecia 
(sp. ?), Nyctipithecas, Chrysothrix sciurea (three specimens). 
(ii) In none of these were any lunulae to be found. 
(lii) We found the cyamella definitely in Hapale jacchus, Jacchus auritus, 
in two other specimens of Jacchus (sp. ?), in Midas ursulus (two specimens), M. 
inidas, M. auritus. 
We could not definitely assert its absence in Cebus or Pithecia, or the squirrel 
monkeys, as the material was less complete. 
The case of Ateles is also doubtful ; two specimens were examined, in neither 
was a cyamella found ; one possessed no fabellae and the other only an internal 
one. This may be due to rough usage, or it might emphasise the correspondence 
with the gibbons which Pearson and Bell noticed in considering the femur of Ateles. 
While we sheuld have anticipated finding lunulae in the more primitive types 
of Cebidae, we have not done so, and conclude that the lunulae were lost to the 
Primates except as occasional anomalies before the separation of Simiadae and 
Cebidae. The chief difference between the apes of the New and Old Worlds 
is that the Cebidae (except in the possible case of Ateles) have never progressed 
to the stage of the Hylobatinae with loss of cyamella and to the stage of the 
Anthropoidea with loss of fabellae as well. 
Lemuroidea. We natui-ally turn with much interest to the prosimian group; 
for the sesamoids of the knee-joint in their case ought to link up with those of 
the Rodents and Insectivores and the test of this will clearly be the occasional or 
persistent occurrence of lunulae in one or more species. 
Here again the expense of procuring moist material, especially when it is to be 
investigated only for a single point in as wide a range of species as possible, has 
much handicapped our work*. 
We turn first to the lemurs proper and notice the following remarkable 
resultsf : Both fabellae, the cyamella and the lateral anterior lunula were found 
in Lemur varia, L. catta, L. melanocephalus, L. coronatus, L. macaco leucomystaxl. 
There is no doubt therefore that the Prosimia add the lateral anterior lunula 
to the fabellae and cyamella of the Simiadae. See Plate XXVII, Figs. 70 and 73. 
Turning to Galago we have found : Galago alleni, both fabellae, the external 
very large, the cyamella and the" lateral anterior lunula. G. crassicaudata ex- 
* The aid given by the Government Grant Committee to the Study of Pearson and Bell on the 
femur, for the purchase of primate material, has of course aided us. 
f Meckel notes merely the existence of both fabellae in L. mongoz, and L. albifrons. Gruber states 
that Stenops tardii/radus lacks both fabellae but has a large articulating sesamoid in the tendon of 
31. popUteus. 
X Femora without the semilunars of L. rubiventer, L. niger, and L. macao varius showed both 
fabellae and in the first case the cyamella also remained. 
