THE FOSSIL FOOTMARKS OF THE UNITED STATES. 221 



Remarks. — The second species of this genus was described by 

 me in 1840, in my Massachusetts Report, with figures, (Plate 

 48, figs. 44, 45,) under the name of Sauroidichnites Barrattii. 

 The evidence then discovered did not prove it to be a quadruped, 

 although I strongly suspected this must be the case. The other spe- 

 cies, the A. scambus, was first described by Dr. Deane, as a quad- 

 ruped, in the American Journal of Science, Vol. XLIX. p. 80, and 

 re-described in the same work, New Series, Vol. III. p. 78. Dr. 

 Deane, however, has represented the hind leg as wanting altogether 

 in a foot, and the lower leg as doubled down upon the long tarsus, 

 or heel ; and he supposes that from the animal's " peculiar organ- 

 ization, one set of feet did not touch the earth " (American Jour- 

 nal of Science, Vol. XLIX. p. 80). Having carefully examined 

 the original specimen from which his drawings and description were 

 taken, belonging to T. Leonard, Esq., of Greenfield, as well as 

 others in Mr. Marsh's cabinet and in my own, I cannot doubt that 

 the hind foot is most distinctly represented in nearly every case, 

 as I have shown it on Plate 13, figs. 1 and 3, and on Plate 21, 

 fig. 1, and on Plate 21, fig. 3, though as to the fourth toe I am 

 not certain ; and the heel of the hind foot has sometimes a pecu- 

 liarity of structure, which might readily suggest the idea of the 

 lower leg folded upon the tarsus ; but I am not prepared thus to 

 explain the slight longitudinal ridges we sometimes find upon it. 

 But, however that may be, I cannot doubt that the hind foot had 

 three stout, very distinct toes, very much resembling some of the 

 tridactyle feet already described ; for I find them on nearly every 

 specimen I have seen ; and although we might say of one instance, 

 that the heel happened to come in contact with a track of Bronto- 

 zoum directly before it, we cannot thus explain the numerous cases 

 exhibited upon the plates above referred to ; the originals of which 



