NO. 8 GRAND CANYON FOSSIL FOOTPRINTS GILMORE J 



formation, indicates that its affinities fall within that genus. Its 

 specific distinctness, however, is shown by its much smaller size, in 

 having the bifurcated toes on the manus, and the more slender form 

 of the toes as a whole. 



The species is named in honor of Dr. David White who collected 

 the type specimen. 



PARABAROPUS COLORADENSIS (LuU) 



Plate I 



Megapezia ? coloradcnsis Lull, R. S., Amer. Journ. Sci., Vol. 45, 1918, p. 341. 

 Parabaropus coloradcnsis (Lull), Gilmore, C. W., Smithsonian Misc. Coll., 

 Vol. 80, No. 3, 1927, p. 53. 



On the track covered surface of a large slab (No. 11,707, 

 U. S. N. M.) of impure Hermit sandstone of the collection of 1927, 

 obtained from the fossil track locality one-fourth mile west of the sign 

 " Red Top " on the Hermit Trail, is a trackway identified as Para- 

 baropus coloradcnsis (Lull). This trail, the most perfect yet dis- 

 covered, shows the trackway to have a width of about 190 mm. 



On this same slab are numerous trails of Holopus licnnitaniis and a 

 single trackway of CoUcttosanrns, probably C. pcntadaclylns. The 

 large size of this slab, with its undulating surface covered with foot- 

 prints, presents an interesting section of the old mud flat over which 

 these animals walked and which has preserved a plain record of their 

 ramblings. A view of this specimen is given in plate i. 



The stride of the Parabaropus tracks' varies from 260 to 340 mm., 

 whereas in specimen No. 11,598, described in my previous paper,' the 

 stride is about 240 mm., and it is quite apparent from the measure- 

 ments of the foot impressions that the two animals were of about the 

 same size. 



In the specimen now before me. the pes impressions lack the 

 elongated sole which is such a distinctive feature of the hindfoot in 

 the tracks previously referred to.' The difi:'erence noted is due, as 

 is clearly apparent from a comparison of specimens, to the difference 

 in depth to which the feet impressed themselves into the mud. In the 

 specimen under discussion, the posterior part of the heel did not regis- 

 ter, whereas in the trackway previously described, the whole foot sank 

 deeply into the muddy surface. The proportions of the feet, number 

 of toes, their form and close similarity of arrangement, leave no 



* Fossil footprints from the Grand Canyon, Smithsonian Misc. Coll., Vol. 80, 

 No. 3, 1927, p. 57. 

 ' Op. cit., p. 56, fig. 27. 



