10 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 8o 



lengths : 11= 15 mm., 111= 17.5 mm., IV= 15 mm., ¥ = 7.5 mm. Hind- 

 foot regnlarly placed in front of fore, bnt usually clear of the toes 

 of the manus. Forefoot: Length about 30 mm., width about 30 mm. 

 Four toes. Toes lengthening toward the outside of foot, the outer and 

 inner being short and subecjual in length. The outer toe originates well 

 backward on the side of the palm, and is directed forward and out- 

 ward. Median toes widely separated and divergent anteriorly. All 

 of the digits of the manus have subacute terminations (see fig. 4). 

 The foot as a whole is much smaller than the "pes. Sole relatively 

 short, being broader than long and broadly but regularly rounded 

 posteriorly. Length of toes as follows: 11 = 7.5 mm., Ill = 12.5 mm., 

 IV=I4.5 mm., V = 7.5 mm. The digital formula of five and four 

 at once distinguishes this genus from all described forms of the Supai 

 ichnite fauna. Batrachiclinus of the Hermit, Laoporus and Agostopus 

 of the Coconino, have a similar number of toes, but here their resem- 

 blance to Annnobatrachits largely ends. The intermediate size of the 

 footprints under discussion, the wide spreading of the toes, and dif- 

 ferences in length and other proportions effectually distinguish these 

 from all other Grand Canyon tracks. 



Hickling * figures a pes track from the Permian of Corncockle Muir, 

 Scotland, which bears certain resemblances to the pes, but his details 

 of foot plan are uncertain and thus a closer comparison is of little 

 importance. 



INVERTEBRATE TRAILS FROM THE SUPAI FORMATION 



During the field work of 1927, a considerable number of trails 

 evidently made by invertebrate animals, were observed in the track- 

 bearing horizons of the Supai formation. Owing to the lack of proj^ier 

 facilities, only a few of these were collected. Although many of them 

 clearly show that the impressions were made by animate creatures, 

 their details are not sufticiently clear to depict their principal charac- 

 teristics, and on that account they seem unworthy of generic and 

 specific designation, but in order to advance our knowledge of the 

 Supai ichnite fauna as far as is consistent with the character of avail- 

 able materials, a few of these specimens are briefly described and 

 illustrated. 



In figure i, plate 4, is illustrated a trail (No. 11,740, U. S. N. M.) 

 found lying on the slope west of O'Neill Butte. A second specimen 

 found later on a massive block of sandstone at the base of the track- 



^ Manchester Lit. and Philos. Soc, Memoirs and Proc, Vol. 53, 1909, Art. 22, 

 pp. 6 and 7, pi. 3, fig. 20. 



