Nov., 1846.] 121 



the analysis of some of the coprolites found iu the valley is pretty 

 conclusive evidence that birds did exist there at the time the sand- 

 stone was forming. 



Now if we take the Crocodile, Alligator, or any of the Saurian 

 type with which we are acquainted, we should expect to see their 

 tracks made at irregular intervals, and at some distance on either 

 side of a plane passing perpendicularly through the centre of 

 gravity of the animal in the direction of its motion, especially 

 when we consider the width the feet are separated, and the 

 clumsy manner in which these animals must move. These ani- 

 mals would, in all probability, leave the print of a portion of the 

 leg next the foot, and which, if I mistake not, is the case with the 

 fossil tracks acknowledged to be of the Sauroid character, found 

 in the same valley. " 



Dr. Morton concluded the reading of his memoirs on u Hybridity 

 in animals considered in reference to the question of the Unity of 

 the Human Species," and after some general remarks, submitted 

 the following conclusions : 



1. A latent power of hybridity exists in many animals in the 

 wild state, in which state, also, hybrids are sometimes produced. 



2. Hybridity takes place not only among different species, but 

 also among different genera ; and the cross-breeds have been 

 prolific in both cases. 



3. Domestication does not cause this faculty, but merely 

 evolves it. 



4. The capacity for fertile hybridity, cceteris paribus, exists 

 in animals in proportion to their aptitude for domesticity and culti- 

 vation. 



5. Since various species of animals are capable of producing a 

 fertile hybrid offspring, hybridity ceases to be a test of specific 

 affiliation. 



6. Consequently, the mere fact that the several races of man- 

 kind produce, with each other, a more or less fertile progeny, 

 constitutes, in itself, no proof of the unity of the human species. 



