EVOLUTION OF THE SKELETON OF EOCENE AND OLIGOCENE TITANOTHERES 



683 



phalanges are carried on the plantar side of the prox 

 imal, there being apparently a sharp flexure between 

 them. The distal phalanges are very narrow and 

 but slightly expanded at the extremities, the trans- 

 verse measurements being, II, 30 millimeters; III, 



30+ ; IV, 28. 



Menodus trigonoceras 



Referred manus and pes 



The reference of the pes of Menodus trigonoceras? 

 (Am. Mus. 1079) to the genus Menodus is confirmed 



more primitive stage of M. Tieloceras and relate it to 

 the more progressive stage which we suppose to be that 

 of M. trigonoceras. All the dimensions of the pes are 

 larger, and the bones of the tarsus are decidedly 

 broader and flatter; the summit of the tuber calcis 

 is of more flattened or elongate oval section; the 

 cuboid is relatively broadened and flattened, and 

 Mts III is broadly articulated with it by displace- 

 ment, and the proximal phalanges, especially those of 

 D. 3 and D. 4, are shorter. 



Figure 615. — Restorations of Menodus trigonoceras (A) and Allops marshi (B) 

 Not drawn to scale. A is baseiS on the mountei skelston in the Munich Museum and is about one twenty-second natural size (6 feet 5 inches). 



by the presence of all the generic characters already 

 enumerated, as found in the pes referred to M. 

 lieloceras or M. proutii — namely, the slender, rounded 

 shaft of the tuber calcis, the narrow, obliquely directed 

 sustentaculum, the reduced cuneiform, the relatively 

 slender Mts II with the sharp ridging and grooving of 

 the superior portion of its shaft, the small size of the 

 terminal phalanges, the laterally compressed cuboidal 

 facet. We note, however, several important progres- 

 sive characters in this pes, which remove it from the 



The calcaneum measures 155 millimeters vertically; 

 the combined distal astragalar and calcaneal facets 

 measure 105 millimeters transversely; the navicular 

 is decidedly more flattened (vert. 22, tr. 53) ; the cuboid 

 also is more flattened (vert. 36, tr. 57), but it still 

 exhibits a narrower astragalar (27) than calcaneal (42) 

 facet; the mesocuneiform is distinctively small (tr. 

 23, ap. 43). Mts II is readily distinguished by its 

 anterior median ridge bordered ectally by a groove; 

 it measures 173 millimeters vertically; it exhibits a 



