196 AN ATTEMPT TO DESCRIBE THE ANIMALS THAT MADE 



acter in this animal. The hind toe, it will be seen, stands at near- 

 ly right angles to the axis of the foot ; not on a posterior prolonga- 

 tion of the outer front toe, as is usual in four-toed living birds, and 

 in most species of Ornithopus. 



Affinities of the Group. — The same characters which ally the 

 last group to birds exist in this also. We have, in addition, a hind 

 toe, situated as in many of the four-toed birds ; so that its impres- 

 sion on mud lies on a posterior prolongation of the outer toe. 

 Furthermore, in one species at least (the O. gracilior), we have 

 proof that the hind toe was articulated high upon the tarsus, so 

 that only its extremity reached the ground, as is the fact with many 

 birds. So that, in the present group, the relations to birds are 

 stronger than in any of the other leptodactylous species. We have 

 proof that some fossil animals, with tridactylous feet, were quad- 

 rupeds, and probably some bipeds were batrachians ; but I know 

 of no example in living or fossil nature in which a biped with four 

 toes, situated as in this group, was any thing else than a bird. 



Table of the Ratio betiveen the several Characters of this Group, on 



a Scale of 100. 



