THE FOSSIL FOOTMARKS OF THE UNITED STATES. 243 



Species 1. Ancyropus heteroclitus. (PI. XV. Figs. 3 - 5.) 



Sauroidichnites heteroclitus and Jacksoni, Mass. Gaol. Report, 

 Plate 30, figs. 2 and 3. 



Nos. 2-6, 130, 156, in Cabinet. 



Hind foot. — Heel 1.5 inch long, 0.7 inch wide. Length of the 

 inner toe, 0.4 inch ; of the second, 0.6 inch ; of the third, 0.5 

 inch ; of the hind toe, 0.5 inch ; of the foot, 3 inches; of the step, 

 from 4.5 to 5.6 inches. Versed sine of the outward curvature of 

 the toes, from 0.4 to 0.7 inch, making them very crooked. Dis- 

 tance from tip to tip of the lateral toes, 0.9 inch ; of the inner and 

 second, 0.45 inch ; of the second and third, 0.45 inch ; of the 

 middle front and the hind toes, 1.8 inch. Heel at its posterior ex- 

 tremity adhering to the mud so as to raise a singular conical emi- 

 nence (shown in the drawings), as it was lifted up. Tracks in 

 two rows, from 6 to 7 inches apart ; the toes turned outward, and 

 the axis of the foot parallel to the line of direction. 



Fore foot, — Heel 1.8 inch long, and 0.3 inch broad ; crooked ; 

 the hind part turned towards the line of direction, opposite to that 

 of the toes. Length of the inner toe, 0.3 inch ; of the middle, 

 0.4 inch ; of the outer, 0.35 inch. Perhaps a fourth toe on the 

 inner side of the heel. Distance from tip to tip of the lateral toes, 

 0.5 inch ; of the inner and second, 0.3 inch ; of the second and 

 third, 0.25 inch. Curvature of the toes the same as on the hind 

 foot. Tracks of both the hind and fore feet shown, of the natural 

 size, on Plate 15, figs. 3-5 ; the last two being of the hind foot. 



Remarks. — Until recently I had found only insulated tracks of 

 this genus, and I described the hind and fore feet as distinct species 

 (Geological Report, p. 478, Plate 30, figs. 2 and 3). The discov- 

 ery of the specimen of tracks from which Plate 19, fig. 4, was 

 sketched, however, although quite imperfect, reveals the true char- 



