THE FOSSIL FOOTMARKS OF THE UNITED STATES. 235 



in fact a digitigrade impression of the Macropterna. But since the 

 toes of the former are much more divaricate and curved than those 

 of the latter, I do not give in to this opinion, and have retained the 

 former as a species. The specific name of the Macropterna is 

 founded upon the fact that the rhynchosaurus, according to Mr. 

 Ward, had but three toes in front, although a saurian lizard. 

 Although the fore foot frequently shows a heel, I have found one 

 on the hind foot in only two instances. Yet they are very distinct 

 examples ; though I cannot understand why it should not be shown 

 in other cases, where the foot made as deep an impression. But I 

 have seen too many similar omissions in other tracks, whose char- 

 acters are well known, to be surprised at it. 



The fourth toe on the hind foot I have found in only one in- 

 stance ; and in that case only the extremity of the toe reached the 

 ground ; this may explain why it left an impression so seldom. 

 The specimen is so distinct, that I can hardly doubt the existence 

 of such a toe on the animal. 



The figures of this species, on Plate 22, are all copied from speci- 

 mens, and are reduced to one third of the natural size. 



Locality. — Wethersfield, on red shale ; also at the Horse Race, 

 in Gill, on fine gray micaceous sandstone ; and at South Hadley, 

 on gray micaceous sandstone. 



Species 2. Macropterna recta. (PI. XV. Fig. 6.) 



Sauroidiclmites palmatus, Mass. Geol. Report, Plate 34, fig. 15. 



Nos. 31-33, in Cabinet. 



Hind foot. — Tetradactylous, leptodactylous, plantigrade. Di- 

 varication of the outer toes, 75° to 80° ; of the inner and second, 

 10° ; of the second and third, 30° to 35° ; of the third and fourth, 

 35°. Length of the inner toe, 0.9 inch ; of the second, 1.25 inch ; 



