Grand Canyon of the Colorado. 343 



mud-crack, the slab being in relief, so that the true out- 

 line, especially of the distal end, is conjectural. The 

 other digits are each of them clawed, but have been sub- 

 ject to a crushing over toward the outer aspect of the 

 hand so that their outline in the drawing is not natural, as 

 no attempt has been made to ''restore" them to their 

 original condition. The outermost digit diverges some- 

 what more, the third and fourth a little less, and the 

 second and third least of the four. The palm is well 

 impressed and, were it not for the mud-cracks, doubtless 

 its entire outline would be seen. 



Pes : The foot is broad-soled, with four or five diverg- 

 ing digits terminating roundly, without indications of 

 claws, and the well-rounded sole is impressed; both hand 

 and foot are therefore plantigrade and approximately 

 equal in extent. 



The trackway is broad, indicating a wide-bodied 

 animal. 



Dimensions. 



Manus. 



mm. 



Length 55-8 



Breadth from tip of digit i across palm ?44-0 



Length of digit i ?17-0 



" " ii 27-5 



" " iii 300 



" " iv 25-0 



" " v 270 



Between tips of digits ii and v 37-5 



Pes. 



Length 48-5 



Breadth . .' 500 



Length of digit i 12-6 



" " ii 150 



" " iii 170 



" " iv ?15-5 



"Width of trackway '. c. 1400 



Except for the acuminate claws of the hand and the 

 apparent presence of a fifth digit in the pes, this 

 form comes nearest to the genus Megapesia from the 

 Lower Carboniferous shales of Parrsboro, Nova Scotia, 

 described and figured by Matthew. 4 The long stride is 



4 Op. eit., p. 102, pi. II, %. 4 a, b. 



