1898.] Wortman, Extinct Camelidce of North America. 1 09 



only. That part of the shaft which is preserved is very slender 

 and closely applied to the shaft of the tibia. In the hind foot the 

 tarsal bones have nearly the same relations as in Pocbrot/ieriuni. 

 The tuber of the calcaneum is somewhat shorter proportionately 

 than in the White River genus, but otherwise both the calcaneum 

 and astragalus are strikingly alike in the two genera. The cuboid 

 of Protylopiis is slightly narrower in proportion to its height than 

 the corresponding bone in 

 Poebrothcriuiii.1 and the navi- 

 cular is provided with a 

 much better developed pos- 

 terior hook. As in Poebro- 

 theriion, there are two cunei- 

 forms present, the inner of 

 which is a vestigial nodule 

 of bone only. 



There are but two func- 

 tional raetapodials, the third 

 and fourth, the second and 

 fifth being reduced to mere 

 vestiges. Upon one side the 

 vestige of the second meta- 

 podial is preserved in place, 

 and it is seen to articulate 

 by a peculiar ledge-like facet 

 upon the principal cunei- 

 form. Upon its posterior 

 surface is a distinct facet 



by which it articulates with the small cuneiform. The remnant 

 of the fifth is not preserved, but the facet by which it articulates 

 with the cuboid is very small, and there can be no doubt that it 

 was as much reduced as the second. 



The functional metapodials are relatively much shorter than 

 in Pot'brot/ierium, and of a considerably more primitive form. 

 They are well flattened upon their opposed surfaces in the upper 

 half of the extent of their shafts. Below this the inner surfaces 

 of the two bones are well rounded. Unlike the metapodials of 

 Pocbrotheriiim, they lack that characteristic four-sided appear- 



Fig. 5. Left hind foot, femur, tibia and fibula 

 oi Protolypiis petersoni (y.). caL, calcaneum ; as.., 

 astragalus; cb., cuboid; «<!., navicular; cw^., ex- 

 ternal cuneiform; /«., head of femur; /r., greater 

 trochanter; tr"^.^ lesser trochanter; /., tibia ;yi^., 

 fibula. 



