PAL^OMASTODON. 147 



the condyles {i.e., o.c.) are subequal, as in E. maccimus ; they are separated by a deep 

 intercondylar fossa, which extends into the inner face of the condyles and is crossed 

 obliquely by a ridge running down from the upper inner end of the outer condyle. 

 The trochlear surface is too much broken in this specimen for description. 



A left tibia (PL XVI. figs. 4, 4 a) from the same locality is, on the whole, like that 

 of the Elephant. It is, however, rather more slender in the shaft, and the distal 

 articulation differs in several important points. At the proximal end the articular 

 surfaces are somewhat more obliquely placed than in Elephas, the inner facet (1) being 

 somewhat more elevated with regard to the outer (o.) ; the two facets are of nearly equal 

 size. The upper end of the cnemial crest (en.) is slightly more prominent in proportion 

 to the thickness of the shaft than in the Elephant, and both in this and in the other 

 points mentioned there seems to be a greater likeness to the tibia of Tetrahelodon. 

 On the middle of the front of the shaft there is a vertical groove-like depression for 

 the insertion of a muscle. The distal end differs from that of the tibia of Elephas in 

 the following points : — (1) the internal malleolus (i.m.) is much more prominent and 

 is sharply bounded on its astragalar side by a well-defined groove ; (2) the astragalar 

 surface is more strongly concave from before backwards and posteriorly is produced 

 downwards into a prominent point near its inner side ; (3) the surface for the fibula is 

 smaller and situated further back. The whole surface indicates that the tibial face of 

 the astragalus was narrower and more convex from before backwards and interlocked 

 much more closely with the tibia than in. Elephas ; the broad, gently convex, tibial 

 surface of the astragalus in the later Proboscidea not being a primitive character of 

 the group. Immediately above the internal malleolus there is on the postero-internal 

 face of the shaft a short deep groove, bounded internally by a strong ridge : this is 

 wanting in the tibia of Elephas. 



No bones of the foot were found with the limb-bones just described, but a single 

 calcaneum (text-fig. 51), from some distance off, so nearly resembles in essential 

 characters the calcaneum of the later Proboscideans, more particularly of the Lower 

 Miocene Tetrahelodon angustidens, that it may be safely referred to Palmomastodou, 

 and from its large size probably belongs to P. beadnelU. 



As might be expected in an animal considerably more lightly built than Elephas, the 

 calcaneum is more elongated, the tuher calcis [t.c.) especially being less short and stout. 

 In its general proportions this calcaneum more nearly resembles that of Tetrahelodon 

 angustidens ; but even in this Lower Miocene form the bone is already considerably 

 shorter and stouter. There is a large fibular facet much like that seen in the 

 calcaneum of Elephas, except that, instead of narrowing gradually from before 

 backwards, it terminates posteriorly abruptly in a nearly vertical border ; it is convex 

 from before backwards and looks upwards and outwards. Of the two surfaces for the 

 astragalus the ectal (ec.) is the larger ; it is nearly flat, only rising a little towards the 

 anterior part of its outer border, where it meets the upper edge of the fibular surface. 



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