twexhofel: expedition to the Baltic provinces. 337 



eral unreliability of unscientific statements relating to locality, how- 

 ever, gives to the above data no other value than that it should be 

 kept in mind in future explorations on Moon.^ 



Time Equivalents of the Silurian Formations. 



Until the fossils have been carefully studied all correlations must be 

 merely tentative and based on published lists and field-identifications. 

 While the conclusions reached may contain something of error, it does 

 not appear likely that the probability of error is very great. 



The Silurian faunas of Esthonia do not appear to have nearly so 

 much in common with the North American faunas of the same time, 

 as existed between those of the highest Ordovician beds of the two 

 countries. The common Russian Silurian corals are largely the same 

 as those of North America, buf that has little meaning as all of them 

 are long ranging. The gastropods and pelecypods are decidedly dif- 

 ferent, the Bryozoa have been subjected to little comparative study, 

 so that reliance must chiefly be placed on the trilobites and brachio- 

 pods. As with the Ordovician, comparison will be made with the 

 Anticosti section. 



The Addifer formation affords the best points of contact for therein 

 Atnjpa reticularis, Eospirifer radiatus, Pentamerus estonus, and Syringo- 

 pora bif areata make their first appearance. In the Anticosti section, 

 these species or their equivalents, appear for the first time in the very 

 topmost portion of the Gun River formation and are typical of the 

 Jupiter River. Using first appearances as a point of departure, leads 

 to the correlation of the Addifer formation with possibly the upper- 

 most zone of the Gun River and certainly the lower and middle por- 

 tions of the Jupiter River, that is, Clinton. One, however, notes the 

 conspicuous absence of such common Clinton forms as Coelospira 

 hemispherica, the Stricklandinias, and Bilobites bilobus, as well as 

 others not so commonly occurring. 



The Tamsal formation would then be represented by the middle and 

 perhaps the lower portions of the Gun River formation; but, corals 

 excepted, there is little specific faunal evidence supporting the correla- 

 tion. The general aspect of the fauna, however, is not so old as that 

 of the Becsie River faunas. A conclusion can be reached if the faunas 

 of a region intermediate in position be selected for common comparison. 



' Schmidt. Mem. Acad. imp. sci. St. Petersb., ISSl, ser. 7, 30, no. 1, p. 49. 



