214 



AYERS. 



[Vol. VI. 



form of the Sauropsid organ, it is only among the higher mem- 

 bers of the class of Saurians that it is found, while among the 

 birds the organ is not so fully differentiated as it is in the 

 Saurians, and it is not intended to show by the diagram that 

 the Sauropsid organ increases in value or is even present in 

 birds in such perfection as it exists in the higher Reptilia. 



