192 Annals of the Carnegie Museum. 



The Tibia (Fig. 32). — The tibia is, as stated above, short and heavy, 

 which is also characteristic of Merycochcerus, as pointed out by Matthew 

 {Mem. Am. Mus. Nat. Hist., Vol. I, p. 409, 1901). The head is 

 much expanded both antero-posteriorly and transversely. The spine 

 is relatively heavier than in Merycoidodon and the tendinal groove on 

 the external margin of the head is smaller. The anterior face of the 

 head has a deep, triangular, and rough excavation for ligamentary 

 attachments, which extends well down on the cnemial crest. The latter 

 is very prominent, extends well down, and strongly overhangs the 

 external face, imparting a strong antero-posterior convexity to this 

 part of the shaft. The internal malleolus is especially well-developed, 

 much bent outward, and applied closely to a corresponding deep 

 excavation on the internal face of the astragalus. The trochlea is 

 otherwise of the usual Aferycoidodont-type, i.e., with the straight fore- 

 and-aft median ridge, and the very deep external groove, which 

 corresponds with the asymmetry of the upper trochlea of the astragalus. 

 The tibia appears to be proportionally longer and the lateral meta- 

 podials shorter in some species. 



The Fibula (Fig. 32). — -The proximal end of the fibula is much ex- 

 panded antero-posteriorly, very rugose externally, and entirely co- 

 ossified with the tibia. The shaft is slender with a sharp peroneal 

 ridge and the distal end expands rapidly in the antero-posterior direc- 

 tion. Transversely the malleolus is compressed, so as to form a broad 

 rugose external surface, as in the hippopotamus, and internally there is 

 an articular surface for the calcaneum. The calcaneal face is lance- 

 shaped in outline, takes up approximately half of the internal surface 

 near the anterior border, and is succeeded behind by a rough area of 

 considerable extent for tendinal and muscular attachments. 



The Pes (Plate XXXIX, Figs, i and 2).— As has already been 

 pointed out by Professor Scott in the description of the limbs of 

 P. montanus, the tarsus of Promerycochxrus is low, broad, and massive, 

 but otherwise similar to that in earlier genera. The astragalus in 

 particular is low and broad, but not so much so as in the more recent 

 genus Merycochcerus. The calcaneum has a long tuber similar to 

 that in Merycoidodon, but rounder in cross-section. The internal lip 

 of the sustentaculum is prominent, and the posterior face of the shaft 

 just above the cuboid facet is unusually excavated and rugose. The 

 navicular is broader than ordinarily, but otherwise has all the char- 

 acteristics of the Merycoidodonts generally. The cuboid is low and 

 broad, the calcaneal facet smaller than the astragalus, the latter con- 



