332 The Ohio Journal of Science [Vol. XVI, No. 8, 



To make a direct comparison between these two groups of 

 faunas and see just how much the Ordovician relations of the 

 Richmond are neutralized by the Silurian tendencies, 14% of 

 the Maysville species are common to the Richmond, and but 

 one Richmond species goes on up into the Upper Medina or 

 Clinton. 



While 68% of the Maysville genera pass the break into the 

 Richmond, less than 4% of the Richmond genera pass on into 

 the Upper Medina or Clinton. Or, if we add 10 Richmond 

 genera that do not reappear until the Niagara, we still get 

 less than 5% to compare with the 68% of Maysville genera 

 passing into the Richmond. 



The differences between faunas are shown not only in the 

 introduction of new types, but also in the disappearance of 

 old ones. Making new comparisons on that basis, 54 Maysville 

 genera are absent from the Richmond, though 15 of these 

 reappear later, leaving 39 which, so far as the strata have 

 afforded us any knowledge, became extinct at the close of the 

 Maysville. This would be very nearly 23%, and it includes 

 three major groups, the families Pattersoniidae, Anomalo- 

 crinidae and Trinucleidae. 



In the case of the Richmond, we find 136 genera are absent 

 from the Upper Medina-Clinton. But 16 of these reappear 

 later, leaving 119, or over 54%, of the Richmond genera which 

 became extinct, as compared with the 23% in the previous 

 case. And here we have represented the extinction of 14 

 families, to compare with the 3 closing with the Maysville. 



It is because the Anticosti strata are regarded as filling in 

 the stratigraphic break between the Richmond and the Upper 

 Medina, while their fossils fill in the faunal break and give 

 us a faunal transition, that they were not considered in making 

 up the faunal lists here considered. 



Somewhere during Pre-Albion times there must have been 

 evolving all of the species, genera, families, etc., which appear 

 so suddenly and are so radically difTerent from the Richmond 

 forms. These groups, judged by the standards of present day 

 evolutionists, must have required a very long time for their 

 differentiation. It is not to be expected, then, that during 

 all of this time at least a few of the hardier, wide-ranging 

 forms should have migrated around their barriers into the 

 Richmond sea? Broad diastrophic oscillations began in the 



