40 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 8o 



A salamandroid feature of the feet is seen in the inward toeing of 

 the forefeet and the more outward direction of the toes in the hind- 

 feet. The widely radiating toes of the forefoot and the digital formu- 

 las of 4 and 5 are particularly characteristic of the salamander group 

 and it would seem quite prohahle that the affinities of these tracks fall 

 into that group. 



The assignment of this species to the genus Batrachichnus Wood- 

 worth, founded on a specimen from the Carboniferous shales of 

 Massachusetts, is chiefly on the basis of a similar digital formula 

 supplemented by its small size, with slender toes radially arranged. 

 Its original reference to the Mesozoic genus Exocavnpe, as mentioned 

 by Lull, was a tem]3orary expedient and not intended to imply genetic 

 relationship. The different digital formula as now definitely known 

 shows at once that its affinities lie outside the genus Exocaiiipe which 

 has four digits in the pes and five in the manus. 



The type species Batrachichnus plainviUensis shows a decided me- 

 dian groove (see fig. 18) of which there is no indication in B. delica- 

 titki, but in common with Matthew in referring Droniopus celer to 

 this genus, this feature is not here regarded as of great classificatory 

 importance. 



B. delicatitla is distinguished from B. plainviUensis and B. celer 

 by its much larger size, more widely radiating toes, .especially of the 

 forefoot, and lack of sole impressions. Its distinction from the Jog- 

 gins species is rendered difficult because of inadequate illustration and 

 description. 



BATRACHICHNUS OBSCURUS, new species 

 Plate 13 



Type. — Catalogue number 11,529, U. S. N. M. Consists of a trail 

 about 500 mm. in length ; on this same slab are plant impressions and 

 a few tracks of Hylopus sp. 



Type locality. — About one-fourth mile west of the sign " Red 

 Top " on Hermit Trail, at head of Hermit Gorge, Grand Canyon 

 National Park, Arizona. 



Geological occurrence. — Hermit Shale (about 30 feet above 

 Hermit-Supai contact). Permian. 



Description. — Stride 23 mm., width of trackway 23 mm., width of 

 median groove 8 mm. Hind foot: Length 9 mm., width 6 mm. There 

 appear to be five short digits ; third and fourth subequal in length 

 and directed straight forward ; fifth*much shortened but not especially 

 set off from other toes ; second and first progressively shortened 

 inward (see fig. 17). Although the trail is of considerable length 



