206 AN ATTEMPT TO DESCRIBE THE ANIMALS THAT MADE 



quadruped. The shale on which they occur is so brittle that it 

 is difficult to obtain a slab more than a foot long, and then the 

 tracks are so numerous that their interference obscures the charac- 

 ters. When I first opened the rocks at this spot, ten years ago, 

 these points probably might easily have been settled ; but I was 

 not then aware of their importance. I strongly suspect that the 

 tracks of the two species of Tricenopus may be only those of 

 the hind and fore feet of a lizard. I have several specimens, in 

 which two tracks occur almost in the same place, as already fully 

 described. 



Genus X. HARPEDACTYLUS. 



Leptodactylous ; three to four-toed. Toes all curved inward, 

 like sickles. 



Species 1. Harpedactylus gracilis. (PI. XIV. Fig. 2.) 



Sauroidichniies ienuissimus, Mass. Geol. Report, Plate 34, fig. 13. 



Nos. 27 - 30, in Cabinet. 



Divarication of the outer of the three front toes, 70^ ; of the 

 inner and middle toes, 33° ; of the middle and outer toes, 35° ; 

 of the fourth or hind toe and the outer front toe, 55°. Length of 

 the inner front toe, 1.9 inch ; of the middle toe, 2.2 inches ; of the 

 outer toe, 1.8 inch; of the fourth or hind toe, 0.9 inch; of the 

 heel, 1.6 inch; of the foot, 3.7 inches; of the step, 8 inches; 

 of the middle front toe beyond the rest, 0.8 inch. Distance 

 between the tips of the lateral front toes, 2.2 inches; of the 

 inner and middle toes, 1.25 inch ; of the outer and middle 

 toes, 1.5 inch; of the hind and middle toes, 2 inches; between 

 the roots of the front toes and the origin of the fourth toe, 

 0.7 inch. Width of the heel, 0.2 inch. Tarsal joint lifting up 



