46 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 8o 



prints that they cannot all be contained in the genus Hylopus." He 

 then shows that H. hardingi, H. minor, and.//, logani should be re- 

 tained in the genus and at the same time selects H. hardingi as the 

 genotype. He also concludes (p. 85) " that five toe-marks of the 

 hindfoot and four in the fore is the typical number for Hylopus." 

 It is this conclusion that leads him to question the propriety of re- 

 taining //. minor which has a digital formula of 5-5. H. coudifer 

 is removed to the genus Aspcripes, and H. triiidus to the genus 

 Ornithoides. 



Dawson in his characterization and also in his first published fig- 

 ures ' before the species was named, shows five digits on the forefoot. 

 In the light of the many other resemblances to these tracks found in 

 specimens from the Grand Canyon, in which there are five distinct 

 toe impressions on the forefoot, it would seem that Dawson was 

 probably correct, and that Matthew was in error in thinking there 

 were only four toes on the manus. Because of the close resemblances 

 found in these footprints from the Hermit shale to those of H. hard- 

 ingi Dawson, especially in relative length of digits, stride and 

 width of trackway, I refer the following new species to Hylopus, 

 which may now be characterized as follows : 



Generic characters (emended). — ^Quadrupedal, semidigitigrade. 

 Manus subequal or smaller than pes. Five toes in both manus and 

 pes ; toes in both thick with bluntly pointed extremities ; fourth 

 longest, progressively decreasing in length inward ; fifth in both fore- 

 and hind feet much shortened and strongly set off from others. Stride 

 long, hindfoot placed behind forefoot. 



Genotype. — Hylopus hardingi Dawson. 



Matthew also points out that all of the species except H. logani 

 have the print of the sole preserved, and on that account infers that 

 Dawson was in error in regarding the feet as being digitigrade. This 

 conclusion is fully sustained by the semi-])lantigrade character of the 

 impressions of the specimen about to be described. 



HYLOPUS HERMITANUS, new species 

 Plate 15 



Type. — Catalogue number 11,517, U. S. N. M. Consists of a slab 

 on which is a trail showing many of the tracks of both fore- and 

 hind feet beautifully impressed. 



Type locality. — One-fourth mile west of sign post " Red Top " on 

 Hermit Trail, head of Hermit Gorge, Grand Canyon National Park, 

 Arizona. 



'Air-Breathers of the Coal Period, Montreal, 1863, pi. 1, figs. 2, 2a. 



