48 



Proceedings of the Royal Irish Academy. 



three curves in fig. l,tliis curve will give an accurate representation of 

 the changes in the character of the fauna, as a whole, during the same 



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Species. 3 





Figure 1. 



period. In these two diagrams we observe the high northern character 

 of the Eallyrudder fauna. A rapid dying out of Arctic and northern 



Figure 2. 



species leaves the fauna of the boulder-clay still with a distinctly 

 northern aspect. The high northern species now all disappear, and 



