Grand Canyon of the Colorado. 341 



Schuchert slab Noble slab 



mm. mm. 

 Pes. 



Length 22 c. 24-0 



Width 31 c. 28-5 



Digital lengths unobtainable. 



Length of stride 112 av. 1300 



Width of trackway 1000 



Doctor G. F. Matthew in his paper An attempt to 

 classify Paleozoic batrachian footprints 9 arranges the 

 known Paleozoic ichnites under eleven groups, the crite- 

 ria being the number of toe marks impressed, also the 

 general form, whether broad or slender, heeled or heel- 

 less, and so forth. According to his scheme, our genus 

 would fall into group seven, Limnopus, to which, as we 

 have seen, it bears the greatest resemblance. The 

 present genus differs from Limnopus, however, in the fact 

 that the impressions of fore and hind feet do not inter- 

 fere, whereas in Limnopus that of the pes always over- 

 laps the manus. The latter genus shows no trace of claws 

 and the digits terminate roundly instead of being 

 acuminate as in Laoporus. Furthermore the digits in 

 Limnopus are more distinctly separated at their base. 



Megapezia (?) coloradensis, n. sp. 

 (Plate III, fig. 2; text fig. 3.) 



In addition to the above described forms from the 

 Coconino sandstone, there are several other specimens in 

 the Schuchert collection from an older horizon, the Upper 

 Supai of Hermit trail in the Grand Canyon. In this lot 

 there are several specimens representing at least two 

 species which vary exceedingly in size as well as in other 

 details of structure. They pertain to unknown species 

 and probably to undescribed genera of Paleozoic ichnites. 



The larger species is impressed upon three small slabs 

 of red impure sandstone, one apparently of the manus 

 obscured by crushing and mud-cracking, another of the 

 pes, and a third with two impressions each of hand and 

 foot which determine the width of trackway but not the 

 length of stride. 



Specific characters. — The creature seems to have been 

 five-toed in front and behind; there is, however, some 



3 Trans. Boy. Soc. Canada, 9, pp. 109-121, 1903. 



