444 A. W. GRABAU THE SHERBURNE SANDSTONE 



Pteropoda 



102. Colcolus acicuhuii 



An immigrant from the ^N'aples fauna. 

 106. Styliolina fissurella Hall 



An immigrant from the Xaples fauna. 



Cephalopoda 

 108. Gomplioceras tumidum Hall 



Affinities not ascertainable. 

 112. Goniatites sinuosus Hall 



An immigrant from the Naples fanna to the "west. ' 



115. Orthoceras anguis Hall 



Possibly derived from 0. aidax of the Hamilton, a related 

 though larger species. 



Crustacea 

 122. Mesothym oceani Hall 



Probabh' one of the river phyllocarids of the period. 



Echinodermata 



These are all new forms and, as the crinoid fauna of the Hamilton is 

 still little known, no comparison can be made. 



It is thus seen that, where comparisons are possible, newly appearing 

 species, when not immigrants from the Naples fauna or the western 

 (lowan) fauna, are all referable back to some Hamilton ancestor. This 

 is extremely significant and shows that the connection with the main 

 abiding place of the Hamilton fauna was severed. That this abiding 

 place was to the east is shown by the persistence there in unchanged 

 condition of the Hamilton fauna in post-Hamilton time. I place this 

 center of distribution in the Atlantic. That the Sherburne bar was 

 effective in keeping the new formed fauna out of the eastern area is 

 shown by a comparison of species. That it disappeared as a barrier after 

 the deposition of 250 feet of sandstone is shown not only by the fossil- 

 iferous character of the beds overlying the typical Sherburne of the 

 Chenango-Unadilla region, but also by the fact that then the persistent 



