NO. 3 GRAXD CANYON FOSSIL FOOTPRINTS — GILMORE I3 



Generic characters. — Quadrupedal. Pes long and narrow with four 

 digits ; fourth long, slender and curved outward. Manus smaller than 

 pes, three digits. Toes of both fore- and hindfeet acuminate. Feet 

 turned strongly inward toward line of movement. 



Genotype. — Dolichopodus tetradactylus Gilmore. 



DOLICHOPODUS TETRADACTYLUS Gilmore 



Dolichopodus tetradactylus Gilmore, Charles W., Smithsonian Misc. Coll., 

 Vol. 77, No. 9, 1926, p. 6, pi. 4, fig. I. 



A second series of tracks (No. 11,503, U. S. N. M.) referable to 

 Dolichopodus tetradactylus was found by the 1926 expedition at the 

 Hermit Trail locality and in the same horizon in the Coconino sand- 

 stone in which the type occurred. It is of interest as furnishing 

 confirmatory evidence of the original description and illustration, in 

 addition to throwing further light on the structure of the forefeet, 

 of which the type specimen showed little more than the presence of 

 three sharply pointed digits. The present specimen shows the sole 

 to be narrow and the foot, as a whole, smaller than the hind foot. 

 In the type the hindfoot was placed in advance of the fore, but in 

 this specimen the forefoot impression is usually slightly in advance 

 or at one side of the hindfoot. This placing of the feet, however, 

 may be due to the irregularity of the stride as no two steps measure 

 the same, varying from 160 to 250 mm. in length. None of the tracks 

 of the forefoot gives evidence of more than three toes, although some 

 are deeply impressed. The forefoot, measured from the back of the 

 heel to the tip of the longest toe, has a length of 16.5 mm. and a 

 width in the opposite diameter of 19 mm. The hindfoot has essen- 

 tially the same proportions as the type. A third slab (No. 11,495 

 U. S. N. M.) also has a few impressions attributable to this species, 

 but these are scattered tracks made by the hindfeet and add nothing 

 to our previous understanding of them. 



Genus NANOPUS Marsh 

 Nanopus Marsh, O. C, Amer. Journ. Sci., Ser. 3, Vol. 48, 1894, P- 82. 



Marsh's conception of this genus as set forth in his description of 

 the type species can now, with the discovery of two new species, be 

 greatly emended as follows : 



Generic characters. — Quadrupedal, semiplantigrade. Four digits in 

 pes, three in manus. Manus usually smaller than pes. Toes acumi- 

 nate or bluntly rounded. Lateral toes of pes either shorter or subequal 



