234 AN ATTEMPT TO DESCRIBE THE ANIMALS THAT MADE 



the inner to the second toe, 0.5 inch ; from the second to the 

 third, 0.55 inch ; from the third to the fourth, 0.4 inch (?). 



Fore feet. — Tridactylous. Divarication of the toes essentially 

 as in tlie hind feet. Length of the middle toe, 0.4 inch ; of the 

 inner toe, 0.3 inch; of the outer toe, 0.25 inch ; of the heel, 0.25 

 inch ; of the foot, 0.6 inch. Position of the axis of the foot and 

 distance from the line of direction, same as in the hind feet. Dis- 

 tance from tip to tip of the lateral toes, 0.6 inch ; of the inner and 

 middle toes, 0.3 inch ; of the middle and outer toes, 0.3 inch. A 

 track of the hind foot is always preceded by one of the fore foot, 

 distant usually a little more than an inch. A track of a hind and 

 a fore foot, in their normal position, is shown on Plate 15, fig. 9. 



Remarks. — The track of this remarkable animal was long mis- 

 taken by me for that of Argozoum minimum, and was supposed to 

 be that of a biped, probably a bird. But the discovery of the long 

 heel, and the almost constant occurrence of a large and small track 

 together, showed that it was of quadrupedal origin. It is pos- 

 sible, indeed, that what I call a heel may be a hind toe running 

 directly backwards, as is seen in some birds, and as the track of 

 such lizards as the Phylhirus Cuvieri and Milii would exhibit. 

 (See Dictionnaire Classique d^Histoire Nat., Plate 120.) But its 

 great length on the hind feet makes it more probably, in these 

 tracks, an imprint of the tarsal bone. The specimens from which 

 Plate 22, figs. 4, 5, were sketched were obtained from Wethers- 

 field. That from which fig. 6 was taken was from the north part 

 of South Hadley ; and is given in my Geological Report on Mas- 

 sachusetts, Plate 42, fig. 30, as a track of Argozoum minimum. 

 Since on this specimen no marks of the heel are visible, the resem- 

 blance of the tracks to those of that biped is very striking ; and has 

 led me into some doubt whether the Argozoum minimum be not 



