NO. 9 GRAND CANYON FOSSIL FOOTPRINTS GILMORE IJ 



lack of phalangeal pads, broad soles and feet turned inward toward 

 the line of movement, with forefoot placed in front of the hind, are 

 all features indicating its affinities with the genus Laoporus. The 

 dimensions of the imprints, width of trackway, and length of stride 

 indicate its closest affinities to be with the smaller of the two de- 

 scribed species, L. schucherti Lull, but the distinct separation of the 

 fifth digit from the fourth of the pes, and the shorter length of 

 digits one and four of the manus appear to show its distinctness 

 from that species. 



A rather indistinct trackway (No. 11,176, U. S. N. M.) collected 

 by Dr. J. C. Merriam at the Hermit Trail locality shows a few hind- 

 foot impressions that, except for their larger size, are indistinguish- 

 able from those of Laoporus coloradoensis, to which species they 

 are referred. (See pi. 7, fig. i, and compare A and B, fig. 10.) 



More abundant specimens may show that L. coloradoensis and 

 L. schucherti are synonymous, in which event, on the ground of 



^. ^- 



Fig. 10. — Laoporus coloradoensis (Henderson). A, Outline of 

 left hind footprint. Type, No. 13,238, University of Colorado. 

 B, No. 11,176, U. S. N. M. The same side. Both f natural size. 



priority, the specific name coloradoensis must be abandoned. For 

 the present it seems best to retain both names, even though they 

 cannot be adequately distinguished. 



Upon examination of the two slabs of footprints (Nos. 14,140 

 and 14,141, Univ. of Colo.) illustrated by Henderson' I am quite 

 assured that they have been properly referred to L. coloradoensis. 

 Specimen No. 14,140 has quite a different arrangement of the tracks 

 in that they form a continuous series not set off in pairs as in the 

 type and other figured specimen. The width of trackway, however, 

 agrees with the other two. The change of gait may have been brought 

 about as Henderson suggests, by the animal creeping up a steep bank 

 where travel was difficult. All details of the imprints on these two 

 referred slabs are obscure. The foot structure is well shown in the 

 accompanying figures, and their proportions are given in the table 

 of measurements. 



^ Log. cit., figs. I and 3. 



