Karl Pearson and Adelaide G. Davin 
369 
sesamoid, a large one, oi' Bradypus lies iu its tendon*, and then says that popliteu6- 
contains no sesamoid in Tamandua, Orycteropus and Dasypus. We feel sure he is 
wrong in the first case, the sesamoid of Tamandua is a cyamella. He is right 
about Dasypus. Owing to the kindness of Sir Arthur Keith it was possible for us 
to dissect a knee-joint of Dasypus sexcinctus; no fahellae were found, and only a 
cartilagenous thickening of the popliteal tendon, which it was not even possible to 
consider as a hemisesamoid-j-. There is no doubt, we think also, that the sesamoid 
in the fossil Megatherium cuvieri in the museum of the Royal College of Surgeons 
is a cyaviella not -a fabella. This fossil possesses also a very fine lateral anterior 
lunula: see Plate XXV, Fig. 60. Owen makes no reference to it, and we have 
not found any mention of it elsewhere. This sesamoid like the cyamella rests on 
the fibular articulating surface, but we consider that it would have been in the 
anteiior border of the lateral semilunar. The so-called " fabella " is a parafibular 
sesamoid, it does not lie in the popliteal sulcus, but the tendon of popliteus would 
pass directly to it ; it is not on the posterior surface but the lateral surface of the 
external condyle. It represents really something anterior to the differentiation of 
parafibula into cyamella and fabella lateralis. 
Windle and Parsons' statements as to the sesamoids of the Edentates, namely 
that the 
(a) Bradypodidae have no fahellae but a cyamella (p. 1010), 
(6) Myrmecuphagidae have no fahellae but a cyamella (p. 1011), 
(c) Manidae have no fahellae but a cyamella (p. 1013), 
{d) Dasypodidae have neiVciGM fahellae nor cyamella (p. 1012), 
seem to us to represent the facts. 
With regard to the Orycteropidae there appears to be some diversity of opinion. 
Humphry in his paper on the "Myology of Orycteropus capensis\ (Aard Vark) " 
states that the three heads oi gastrocnemius arise from the outer and inner condyles 
of the femur and from the head of the fihula,\^( sole US'], and that the two former have 
both sesamoids, i.e. fahellae. Gal ton in his " Myology of Orycteropus capensis"^ men- 
tions only a sesamoid in the outer head of gastrocnemius, and cites Owen (Anatomy 
of Vertebrates, Vol. il. p. 409). He speaks of this fahella as " behind the outer 
condyle of the femur," and seems to think it corresponds exactly to what Meckel 
observed in Gholoepus didactylus " though not mentioned by him in connection 
with this [^gastrocnemius] or any other muscle." This is overlooking what Meckel 
himself wrote about the closer association of the sesamoid with the popliteus (see 
our p. 367)1|. And if Orycteropus really resembled Gholoepus, then it would be a 
* The drawing of the skeleton of Bradypus triilc(ctijlus in Parker and Haswell's Text-hook of Zoologif, 
p. 529, shows the ci/amella and the lunula. 
t In one mounted specimen of Dasypus se.rciurtus facets on the condyles were observed which some 
might interpret as vestiges oi fahellae. 
X Journal of Anatomy and Physiology, Vol. ii. p. 313. 
§ Trans. Linnean Soc. Vol. xxvi. p. 594. 
II Mackintosh ("Muscular Anatomy of Gholoepus didactylus," Pnic. Royal Irish Academy, Vol. ii. 
1875 — 77, p. 75) states definitely th&t poj'liti'us has a \a,rge fahella [i.e. cymuella] in the tendon of origin. 
