Fig. I/. — Palaeopus rcgularis. Type, 

 No. 11,143, U. S. N. M. Diagram of 

 trackway, i natural size. 



26 



Paratype. — Catalogue num- 

 ber 11,144, U. S. N. M. Ob- 

 verse slab on which is a consecu- 

 tive series of footprints 1,330 

 millimeters in length. The re- 

 verse of this series is a slab in 

 the museum at the Grand Can- 

 yon National Park. 



Type locality. — Hermit Trail, 

 Hermit Basin, Grand Canyon 

 National Park, Arizona. 



Geological occiifrence .—Co- 

 conino sandstone (about 150 

 feet above base), Permian. 



Description. — C omparative 

 measurements of the type and 

 paratype show a fairly close 

 agreement except in the length 

 of stride, which is 152 milli- 

 meters in the type and 106 n\ 

 the paratype, the width of track- 

 way being 100 millimeters in 

 lioth. Hind foot: Length, 15 

 mm. in both type and paratype, 

 width, 28.5 mm. in type, 25 mm. 

 in paratype. Stumpy and larger 

 than manus, and with five toes, 

 short and without claws. Di- 

 rected straight forward, often 

 overlapping track of manus. 

 Forefoot: Length of type, il 

 mm., paratype, 10 mm.; width, 

 type 20 mm., paratype 19.5 mm. 

 Smaller and more shallowly im- 

 pressed than pes, and with three 

 • ( ?) toes, short and without 

 claws. Placed directly in line 

 with hindfoot. 



The trail made by this species 

 is distinctive on account of the 

 straight trackway and precise 

 regularity of the imprints, espe- 

 cially those made by the hind- 

 feet. The paratype was origi- 



