346 Lull — Fossil Footprints from the Grand ( 'anyon. 



whose relative position is precisely the same as the 

 termini of the pedal toes in the track described. These 

 marks seem therefore to indicate the impression of the 

 right pes. If so, they give a trackway width of 33 mm. 

 and an estimated stride of the same foot of 42 mm., thus 

 indicating a rather wide-bodied, short-legged form. This 

 form is provisionally included in the genus Exocampe 

 Hitchcock, the species being designated as delicatula in 

 allusion to its delicate proportions. • 



Type specimen, catalogue number 2146, Yale Museum. 



These impressions are surely not reptilian, nor should 

 we call them batrachian as Matthew has done. Until 

 their amphibian character is clearly demonstrated, per- 

 haps it were well to place them under Williston's newly 

 proposed ancestral group Protopoda, which, as he says, 

 are thus far known only by their footprints. 5 



I am indebted to my colleague, Professor Schuchert, 

 for the privilege of discussing these interesting forms. 



Explanation of Plates I-III. 



Plate I. 



Laoporus schucherti, n. sp. Genoholotype, Cat. No. 2143, Yale 

 Museum. One third natural size. 



Plate II. 



Fig. 1. Laoporus noblei, n. sp. Holotype, Schuchert slab, 

 Cat. No. 2144, Yale Museum. One third natural size. 



Fig. 2. Laoporus noblei, n. sp. Paratype, Noble slab, Cat. No. 

 8422, U. S. National Museum. Photograph by L. F. 

 Noble. One third natural size. 



Plate III. 



Fig. 1. Exocampe (?) delicatula, n. sp. Holotype, Cat. No. 



2146, Yale Museum. Two thirds natural size. 

 Fig. 2. Megapezia (?) coloradensis, n. sp. a, manus; b, pes. 



Holotype, Cat. No. 2145, Yale Museum. Two thirds 



natural size. 



Yale University, 24 September, 1917. 



D S. W. Williston, The phylogeny and classification of reptiles, Jour. 

 Geology, 25, p. 42, 1917. 



