Karl Pearson and Adelaide G. Davin 
875 
(vi) The cyamella disappears entirely or almost entirely, being merely repre- 
sented by a thickening of the popliteal tendon at the position where definite 
ossification occurs : noted in some ca«es of Didelphys. 
We have already illustrated (i) and (ii) from individual specimens of the 
wombat and the Tasmanian Devil, (iii) is the more general case of both Tasmanian 
Devil and wombat. It is also the case of Dast/in'us macroarut;, Dasyurus ursinus, 
Perameles nasuta and in some instances of Plniiangista vidpina*. 
Didelphys virginiana is typical for (iv). Our sketch, Plate XXXIII, Fig. 84, 
shows the relative position of fabella and cyamella — they form together when the 
cut ends of gastrucneinius are reunited an articulating link between the head of 
the fibula and the external condyle. The reader must remember that in the natural 
position the limb is much more Hexed than in the sketch. 
(v) Our drawing, Plate XXXIII, Figs. 83 a and 83 6, indicates in Macropas 
the fabella with hemisesamoidal cyainella- 
Our drawings of Phalangista vidpina and Pliascolarctus indicate the nature of 
the lateral side of the knee-joint when there is a single parafibular sesamoid which 
has often been described as a fabella lateralis (see Plate XXXIII, Figs. 85 and 86). 
In mounted specimens of Bettongia- gaiinardi, Hypsiprymims murinus, Peragalea 
lagotisf, Myrinecobius fasciains, we found only a sesamoid attached t(_> the lateral 
condyle. 
Fossil Marsupials shoiving Parafibulae. 
Protliijlacinus putdgonicus ( 'lailosictis Uistratus Diprotodoii aiixlralis 
• , ^ after Shaw and Parker 
From the Santa Cruz Beds, after Sinclair 
The fossil Diprotodon australis\ belongs apparently to class (iii), and shows 
according to Professor Stirling's restoration a large parafibula which would only 
* Our photograph, Plate XXXIII, Fig. 85, shows the combined sesamoid in Vhahmgista. 
t In specimens of Pcragalcti lar/otis and P. leucura the fibula did not articulate with temur, there was 
no ossification in the popliteal tendon, but the lateral. A; /-;e//a was present. 
% See Parker and Haswell, Vol. ii. p. 602, Fig. 1229. The fossil Patagonian Marsupials reconstructed 
by Sinclair show fibular crests (or parafibulae'?). See his plates of Cladosictis histratits and Pivflu/la- 
ciiius patoyonicns. He gives no details, however, on this point. He does say that the patella is ossified 
in the latter. See Proc. American Phil. Soc. Vol. xliv. pp. 73 — 81, Philadelphia, 1905. 
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