1382 MEMOIRS OF THE CARNEGIE MUSEUM 
ment is also seen on the intercondylar ridge of the tibia in Dxodon calkinsi from the 
John Day formation. The articulating surface of the inter-condylar ridge is pro- 
portionately more interrupted than in the Oligocene genus, as the irregular-shaped 
sulcus continues to the posterior border, at which point it entirely separates the ar- 
ticulations of the trochlea. The internal malleolus is rather small; it is compressed 
transversely, does not extend much below the distal end of the fibula, and it covers 
only one-half of the antero-posterior diameter of the trochlea. 
The proximal end of the fibula is well codssified with the head of the tibia. 
Immediately below the head the shaft is separated from the tibia for a distance of 
100mm. ; below this point the fibula, as stated above, is entirely fused with the tibia 
leaving little or no trace of a suture between the two bones, except at the distal end. 
The distal end is much expanded antero-posteriorly and rather compressed trans- 
versely. On the anterior half of the external face is a prominent vertical ridge 
which forms the anterior border of the tendinal groove and extends upward for a 
distance of 60 mm. where the ridge becomes rapidly contracted and disappears on the 
side of the fibular face. Distally the fibula extends well down below the trochlea 
and furnishes a symmetrical appearance to the outline of the distal end of the tibia- 
fibula. 
Kowalevsky in his memoir figures a tibia and a portion of a fibula which was 
found with Hntelodon magnum (37, Pl. XX VII, fig. 33). 
These illustrations, together with the casts of the specimens now in the Carnegie 
Museum, present characters quite similar to those of the corresponding bones in 
the older American forms. The proximal end of the tibia of Hntelodon is possibly 
somewhat more expanded, but this may be due in great measure to crushing, as the 
bone has apparently received some injury laterally. The fibula, which is quite 
delicate, is represented by a portion of the shaft lying closely appressed to the shaft 
of the tibia as figured by Kowalevsky. This bone appears to have been turned end 
about; the lower portion, as seen in the specimen, apparently agrees better with the 
proximal than distal end of the American forms. 
MEASUREMENTS OF TIBIA, 
Mm. 
MN Big ses itohinctine ob cuss pegs 9 exe vene: ler mers te eters ans sabe vacant chemo bornt 450 
ve antero-posterior diameter of proximal end, approximately........... 115 
transverse ee be ee Bt ey cay err ri aay 126 
i es ye pee OUStaige Magen cast Rare ONL 
Ul antero-posterior “ oe a ees a2 2 OD: 
