No. i.] OSTEOLOGY OF PCEBROTHERIUM. 67 



The femur is long, with a slender rounded shaft. The head 

 is nearly hemispherical, set upon a very distinct neck, and has a 

 minute circular depression for the round ligament. The great 

 trochanter is relatively very large and massive, but does not rise 

 above the level of the head, and encloses a deep digital fossa. 

 The lesser trochanter is also prominent, but not much extended 

 vertically. Cope states (No. 7, p. 718) that there is no third 

 trochanter ; but I find what I conceive to be a remnant of it on 

 the outer side of the shaft, a considerable distance below the 

 great trochanter. The distal end is much thickened, and the 

 rotular trochlea very prominent, but narrow. The distal end 

 of the tibia shows a very large internal malleolus, and deeply 

 excavated condyles for the astragalus. The fibula seems to 

 have been complete ; its distal end is much enlarged, and shows 

 a tendinal sulcus upon the outer side. 



The tarsus is typically artiodactyl, and shows considerable 

 differentiation. The calcaneum is long and compressed, with a 

 high fibular facet, a prominent sustentaculum, and a broad sur- 

 face for the cuboid. The astragalus is high and narrow, and 

 has the usual double pulley. The cuboid is also high and nar- 

 row. The navicular is low, especially behind, where there is a 

 relatively large facet for the ento-cuneiform. The meso- and 

 ecto-cuneiforms have coalesced in such a fashion that there 

 seems to be a step cut in the compound bone, caused by the 

 fact that the meso-cuneiform is much lower than the ecto-cunei- 

 form ; and while the proximal surfaces of the two are on the 

 same level, distally the latter projects much below the former. 



Only the third metatarsal is preserved ; but the facets of the 

 tarsus show that the pes was tetradactyl, with the median digits 

 enlarged, and the lateral much reduced. The reduction is so 

 far inadaptive that mt. II occupies the whole of the meso-cunei- 

 form, and is in contact with the side of the ecto-cuneiform. 



The hind limb of Hoviacodon has not been described further 

 'than the statement that the pes has four digits, and that the 

 astragalus is "suilline" (Marsh, No. 20, p. 120; and No. 21, 

 p. 364). In Leptotragulus the proximal end of the femur is 

 broad, with a hemispherical head set upon a long and very dis- 

 tinct neck ; the second trochanter is relatively large. 



The distal end of the tibia has a narrow facet for the fibula, 

 showing that the latter had begun to shift beneath the tibia ; 



