EAELY PALEOZOIC BEYOZOA OF THE BALTIC PROVHsTCES. 37 



affinities with the early Trenton; and (3) that the upper Lyckholm and 

 Borkhohn closely resemble certain divisions of the Richmond group, 

 relations more definitely indicated on the correlation table. I have 

 also pointed out that there is a striking similarity in the lithology of 

 several of the corresponding formations in Russia and America, This 

 resemblance, as also the faunal similarity, is particularly notable in 

 comparing" the Baltic succession with the section in central and 

 northern North America, 



Finally, from a study of the lists given on pages 19 to 25, it will 

 be evident that there are comparatively few fossils of other classes 

 than the Bryozoa and corals common to the two areas. The reasons 

 for this unequal community of species are perhaps to be sought in 

 natural and inherent differences in modes of dispersal pertaining to 

 the several classes. While it is possible that I have recognized too 

 many species of Bryozoa as common to the two areas, it is to be said, 

 on the other hand, that my specific work has been checked up by the 

 foremost authority on fossil Bryozoa. Furthermore, specific discrimi- 

 nation has been carried to a greater degree of refinement than ever 

 before attempted, and this refinement naturally affects all the species. 

 If the species had been less closely drawn, a much greater percentage 

 of those common to the two areas would doubtless have resulted. 

 Respecting the other classes the possibihty is recognized that future 

 and similarly close comparative study will show a decidedly greater 

 community of species, but it seems altogether unlikely that the per- 

 centage will ever approximate that attained by the Bryozoa, 



