148 
TEKTIARY YERTERRATA OF THE FAYtM. 
'I'lio sustontacular facet (sus.) is separated from the ectal posteriorly by a deep groove 
wliich eidarges anteriorly into a deep fossa ; this surface is convex from before back- 
wards and anteriorly it is continued forwards and outwards as a narrow strip along the 
to]) of the anterior edge of the above-mentioned fossa, and in front of this it is continuous 
witli tlie small surface for the navicular which meets it at about a riaht anale. The 
sustentaculum, as a whole, is prominent and sharply defined. The cuboid surface (cuh.) 
Text-fig. 51. 
Left calcaneum of Palceomastodon headnelU : A, from above ; B, distal end. 
cub., facet for cuboid ; ec., ectal facet ; sus., susteutacular facet; t.c., tuber calcis. 
The fibular facet lies immediately outside the ectal facet. | iiat. size. 
is much like that seen in Elej)has, but is narrower and does not extend so far towards 
the inner side of the bone ; it is gently concave. Beneath and to tlie inner side of it 
there is a roughened surface which ventral ly passes into a prominent tuberosity. The 
outer face of the calcaneum is concave from above downwards, while the inner side of 
the tvler calcis is slightly convex, the whole tuber being much more compressed 
laterally than in Elcphas, though perhaps not more so than in Tetrahelodon angnstidens. 
iSo astragalus large enough to have belonged to E. headnelU has been found; but a 
