180 AN ATTEMPT TO DESCRIBE THE ANIMALS THAT MADE 



first species I have only a few specimens ; yet they do not appear 

 as if thus altered from a track of the Brontozoum loxonyz, which 

 most resembles this in shape. The phalangeal impressions are dis- 

 tinct, and the mud must have been a fine, tenacious red clay, such 

 as has left us in other species the most perfect tracks ; even in 

 some instances, the papillaj and striae of the skin. The jEtliyopus 

 minor is a common track, though impressions of its claws are not 

 often well exhibited. Yet when they are shown, they seem to have 

 been produced by a marginal wing. The evidence of a wing along 

 the toes is less obvious in this species. But, upon the whole, I 

 have only sliglit doubts that the feet of these animals (birds) were 

 winged. 



Numerous rows of the tracks of this species are represented on 

 Plate 20, fig. 10, and Plate 23, fig. 3, which give the outlines of 

 slabs (the first in my collection, and the other in that of Mr. Marsh), > 

 containing tracks of other species of animals ; two quadrupeds at 

 least, the Anisopus and Helcura. Plate 24, fig. 3, is the outline 

 of a small slab in Mr. Marsh's collection, remarkable for the great 

 distance of the right and left tracks from the line of direction. 

 Yet that they were made by right and left feet is evident from the 

 number of phalangeal impressions on the toes. It seems difficult 

 to suppose that it is not a distinct species fi-om the A. minor ; 

 although that species commonly walked with feet wide apart. 



Affinities of the Sub-Group. — The resemblance between the 

 tracks of these animals and the feet of the Fulica Americana, or 

 Coot, and of the Grebe or Dob Chick, Podiceps Carolinensis, is 

 striking ; and since other considerations (especially the number of 

 phalanges) ally them to birds, it seems reasonable to conclude that 

 the animals which made these tracks were closely allied to the Po- 

 dicepidae. 



