Peterson : (Jsieologv oi" Oxvdactylus. 465 



shape with a small pit on the emarginate tibial side, similar to that of 

 the llama. 



The Navicular. — The navicular is more nearly like that of the 

 recent Tylopoda than any bone in the tarsus. The astragalar facet is 

 concave antero-posteriorly, with an emarginated fossa in the middle 

 of the bone on the fibular side. On the tibial side is another smaller 

 emargination with a small pit ; and below the pit, is a small tubercle, 

 which extends to the distal face and takes up a large portion of the 

 tibial face of the bone. In the llama this tubercle is almost obsolete, 

 while the camel has it better developed. The postero-inferior rounded 

 facet for the cuboid is as prominent as in the camel and llama. Dis- 

 tally there are two facets, the ecto-mcso-^^ and the ento-cuneiform, the 

 two former are divided only by a low ridge, while the latter is 

 separated, and placed somewhat higher on the posterior portion of 

 the bone and is slightly convex. 



The Ecto-meso-cuneiforin. — The united ecto-meso-cuneiforms are 

 comparatively much smaller, especially antero-posteriorly, than in the 

 recent forms. Proximally two facets are indicated by a shallow 

 groove, while the distal articulation is more continuous and more 

 similar to that of the llama. There is only one facet for the cuboid, 

 the antero-fibular, near the proximal end. The prominent tubercle 

 with the rounded facet at the free end on the fibular side which abuts 

 against the cuboid in Cameliis is entirely absent in O. longipes and 

 the llama. 



The Ento-cuneiform. — The ento-cuneiform is an irregularly shaped 

 sesamoid with a proximal, concave facet for the navicular. Near the 

 proximal end on the anterior face is a rounded pit for articulation with 

 the slightly projecting tubercle on the posterior face of the united 

 ecto-meso-cuneiform. 



Near the distal end posteriorly, there is a strong hook-like ])rocess 

 with a large facet slightly convex in all directions, which articulates 

 with the plantar process on metatarsal IV. In the llama this facet is 

 entirely absent though the tubercle is still present in a rudimentary 

 form. The plantar processes have become more depTessed in the 

 llama and the tubercle on the ento-cuneiform is entirely free. Distally 

 and on the fibular side is a fourth facet for the second rudimentary 

 metatarsal. 



"Scott states that the ecto- and meso-cuneiforms are coalesced in Poebrotherium. 

 Jonrn. Morph., Vol. V, No. I, p. 42. 



