344 Lull — Fossil Footprints from the 



mentioned by Matthew as being indicative of activity. 

 The present specimens, as has been said, give no indica- 

 tion of this, but the hand particularly is suggestive of 

 aggressive use. Another Paleozoic genus which the 

 present form resembles is Hylopus, but in that genus 

 there are only four digits in the manus and five in the 

 pes, the reverse of Megapesia. 



The form now under consideration is provisionally 

 referred to the genus Megapesia, the species being called 

 coloradensis from the locality where it was found, the 

 Grand Canyon of the Colorado River. It is about the 

 size of the type species M. pineoi Matthew, differing 

 therefrom, however, in several particulars, mainly in 

 proportions and the apparent impression of five digits in 

 the pes. The figure of M. pineoi given by Matthew 

 shows no claws in the manus track, but Matthew says the 

 first toe had a strong claw and the others probably had 

 also. The prolongation of the palm into a rounded lobe 

 on the outer side is not in evidence in the present species, 

 although another impression of the hand might have 

 shown an agreement here as well. 



Type specimen, catalogue number 2145, Yale Museum. 



Exocampe (?) delicatula, n. sp. 



(Plate III, fig. 1; text fig. 4.) 



The smallest of the forms collected by Professor 

 Schuchert consists of a very delicately impressed fore 

 and hind foot in relief on mud-cracked red shale. The 

 hind foot is the larger and shows four slightly radiating 

 digits, but no trace of sole. The manus is also appar- 

 ently four-toed, with distinct impressions of terminal 

 claws. The digits radiate more widely, but here again 

 there is no palmar impression. The form may therefore 

 be described as digitigrade. Faint indications which 

 may represent phalangeal limitations may be seen on the 

 second digit of the manus. This form resembles most 

 closely the genus Exocampe of the Connecticut Trias, 

 but is a generalized track which almost any small 

 amphibian, such as a modern salamander, for instance, 

 might make, and while it may for convenience be placed 

 within the mentioned genus, genetic relationship with the 

 creatures that made the tracks so designated is not of 

 necessity implied. 



