6o PATAGONIAN EXPEDITIONS: PALEONTOLOGY. 



emargination of the crista into a shorter and narrower internal portion, 

 which curves dorsally above the sacrum, and a very long and pointed ex- 

 ternal portion ; the acetabulum is large and prominently projecting. The 

 ischium is short and laterally compressed, but quite stout. The pubis is 

 short and depressed and the obturator foramen is large and of longitu- 

 dinally oval shape. 



The femur (PI. XI, fig. 5) has a more equine appearance than any other 

 long bone of the skeleton, though it differs from that of Diadiaphortis 

 merely in being more slender, in the narrower and deeper rotular groove 

 and in the more prominent backward projection of the condyles. 



The patella (PL XI, figs. 6, 6a) is a short and broad, shield-shaped bone, 

 which narrows distally to a bluntly rounded point. It differs from that of 

 DiadiapJiorus in being much less massive and thick antero-posteriorly. 



The tibia (PI. XI, fig. 7) is heavy and considerably shorter than the 

 femur : the spine is low and bifid, with its two parts quite widely sepa- 

 rated ; the cnemial crest is prominent, but short, speedily dying away upon 

 the shaft, and the sulcus for the tendon of the extensor longus digitorum 

 is very deep and conspicuous. The distal moiety of the shaft is of more 

 trihedral, less oval, section than in Diadiaphorus and the astragalar facets 

 are deeper, while the anterior intercondylar tongue is more prominent. 



The fibula (PI. XI, fig. 7) has a much reduced and irregular shaft, with 

 ends which are laterally compressed, but expanded antero-posteriorly. 

 The two leg-bones are in contact only at the proximal and distal ends, but 

 the space between them is very narrow throughout. 



Like all other parts of the skeleton, the pes (Pis. XI, fig. 4 ; XII, fig. i) 

 closely resembles that of Diadiaphonts, with many differences of detail. 

 The astragalus has a trochlea which is slightly narrower in proportion to 

 the length of the bone, and somewhat more deeply and sharply grooved : 

 the neck is relatively longer and is less obliquely directed toward the tibial 

 side : on the plantar surface the facet for the sustentaculum of the cal- 

 caneum is not continued so far proximally and narrows less in the same 

 direction, being of almost uniform width, except near the distal end, where 

 it suddenly widens, making the external border of the facet much more 

 concave than in Diadiaphor^is ; this facet is separated from the ectal cal- 

 caneal facet by a narrower and shallower sulcus than in the latter. 



The proportions of the calcaneum are quite as in Diadiaphorus ; the 

 sustentaculum arises nearer to the plantar border, is not so heavy and has 



