26 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 8o 



rounded behind. The missing toe has been tentatively restored as 

 shown in figure 9. 



The specimen selected as the type is the trackway of a large 

 quadrupedal animal and consists of four imprints from the left side. 

 The tracks are deeply impressed and the softness of the sand at the 

 time they were made is indicated by the flows behind the impressions 

 displaced by the impact of the feet. 



The hindfoot with four toes, in size, shape and arrangement of 

 digits has its closest resemblance to Baropus Icntits Marsh from the 

 Coal Measures of Kansas. It differs in having the forefoot smaller 

 than the hind, sole of pes relatively broader, less elongate, and with- 

 out inner protuberance (compare figs. 9 and 10). In this specimen 

 the hindfoot is placed in front and outside of the forefoot impres- 

 sion, whereas in B. lentus the hindfoot is behind the forefoot. It 

 seems quite probable, however, that the trackway now before me does 

 not represent the norriial walking stride of the animal. That the 

 creature was climbing a slope is evidenced by the position of the slab 

 in situ and also by the mounds of sand behind the imprints, displaced 

 by the pressure of the feet. The weight seems to have been equally 

 distributed between fore and hind limbs, as indicated by the subequal 

 depth of the tracks. 



This form may be distinguished at once from AUopiis ? arizonae 

 occurring in these same beds by its nnich larger size, and the lesser 

 number of digits in the pes. 



Genus AGOSTOPUS Gilmore 



Agostopus Gilmore, Charles W., Smithsonian Misc. Coll., Vol. ~y, No. q, 19J6, 

 P- 23. 



The genus Agostopus was established on well preserved specimens 

 from the Coconino sandstone as exposed on the Hermit Trail section. 

 A slightly emended characterization of the genus follows: 



Generic characters. — Quadrupedal, semiplantigrade, with five digits 

 in manus and four in the pes ; broad soled with either two or three 

 clawed digits in the pes. Feet directed inward, hindfoot placed in 

 front of forefoot impressions. Short limbed, wide bodied. 



Genotype. — Agostopus uiatheri (jilmore. 



KEY TO SPECIES 



Hindfoot with three long acutely pointed digits, all directed forward. 



A. matheri 

 Hindfoot with two long acutely pointed digits, both bent strongly outward. 



A. medius 



