NO. 3 GRAND CANYON FOSSIL FOOTPRINTS — GILMORE 5I 



In figure 24 is shown a diagram of the foot plan of AntJiracopits 

 cllangowensis Leidy from the Coal Measures of Pennsylvania, which 

 displays such striking resemblances to the forefoot of Hylopns hcr- 

 mitanus as to allow the suggestion that with the recovery of better 

 preserved specimens of the Pennsylvanian species they will be found 

 to be congeneric. Through the courtesy of Dr. Witmer Stone, direc- 

 tor of the Philadelphia Academy of Sciences, I have had the oppor- 

 tunity of examining the type of Anthracopus ellangozvensis and find 

 on one imprint a faint suggestion of the presence of a fifth digit, 

 although none of the other five tracks preserved gives any hint of its 

 existence. The evidence is, therefore, inconclusive. The absence of 

 the fifth digit in A. cUaiigoivensis is the only important difiference 

 found in a comparison of these two species, and its absence may be 

 due to its not impressing, a condition observed in at least one track 

 of the ty])e of H. Iieniiitaiiiis. In general form, relative length and 



Fig. 24. — Anthracopus cllaiujowcnsis Leidy. Imprint of the right 

 side. Less than natural size. (After Leidy.) 



divergence of the digits, and sha])e of palmar impression there is 

 great similarity between the two. Attention should also be called to 

 certain resemblances found between H. heniiitanits and Ichniuin 

 sphaerodactyluui described by Pabst ' from the Permian (Tauback) 

 of Thtiringen. In the general plan of the feet there is a striking 

 similarity, though the absence of the first digit in the manus and the 

 heavier toes with l)huitly rotmded extremities in /. sphacrodactyliiin 

 effectually distinguishes it from the Arizona form. 



Genus HYLOIDICHNUS, new genus 



Generic characters. — Quadrupedal, semidigitigrade. Both manus 

 and ])es have five digits. Manus smaller than pes and placed in front 

 of hindfoot. Toes terminated either with pellets or having bifurcated 

 ends. 



Genotype. — Hyloidichmts hi f ureal ii.s'. 



'Pabst, W., Deutsche geol. Cesell, \ ..1. 48, iHg6, pp. 638 and 808, text fig. 2. 



