466 Annals of the Carnegie Museum. 



The Metatarsals. — One of the chief distinctive characters of O. 

 longipes is the fact that the lateral metatarsals 11 and V are a little 

 less reduced than is ordinarily the case in the Loup Fork camels. As 

 in Pocbrothe7'iunO^ metatarsal II has "an enlarged head" with an 

 independent articulation, which in O. hvigipes is comparatively higher 

 than in the llama. The bone is firmly coossified with metatarsal III 

 and is supported by the entocuneiform. Metatarsal V, on the other 

 hand is entirely separated proximally from metatarsal IV and articu- 

 lates with that bone by a small rounded facet near the proximal end, 

 but is not in touch with the cuboid. At the base of the palmar proc- 

 ess of metatarsal IV, the two bones IV and V are fused leaving a 

 peculiar ovate-shaped foramen seen in PI. X, Fig. 4. The functional 

 metatarsals III and IV are a trifle lighter than the metacarpals, but 

 are of nearly the same length, thus resembling very closely the typical 

 Tylopoda According to Prof. Scott, Poebi'otheriuin stands farther 

 removed, having the metatarsals longer and broader than the meta- 

 carpals. 



Metatarsal III is only a very little heavier than metatarsal IV, and 

 the lateral metatarsal II, as above stated, distinctly forms a part of the 

 functional metatarsal, as in the recent genera. Metatarsal III has two 

 facets on the proximal end. The anterior is concave and articulates 

 with the compound ecto-meso-cuneiform, while the posterior facet is 

 situated on the palmar process and is a wide shallow pit for the recep- 

 tion of the peculiar convex facet on the ento-cuneiform. The hook- 

 like palmar processes on metatarsals III and IV have become coossi- 

 fied. These are the only parts of the two bones showing any true 

 coalescence and this is a constant character shown in all specimens of 

 O. longipes in the collection of the Carnegie Museum. Metatarsal IV 

 is lighter than metatarsal III, and they are closely applied to each 

 other with the opposed surfaces slightly rugose and extending to within 

 30 mm. of these distal ends. The shafts have a slight curvature 

 with the midshaft turned backward. Laterally the shafts are nearly 

 straight and but little separated distally. Metatarsal IV has two proximal 

 facets which articulate with the cuboid. The anterior articulates with 

 the corresponding facet on the anterior half of the cuboid. The pos- 

 terior is on the palmar process opposite the facet on the process of 

 metatarsal III. On the tibial side near the anterior face is a small 

 facet for articulation with metatarsal III. Distally, as in the meta- 



"^^Journ. Morph., Vol. V, Part 1, p. 42, 1891. 



