TWENHOFEL: 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, but 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 
Atrypa reticularis, Eospirifer radiatus, Pentamerus estonus, and Syringo- 
pora bifurcata 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. 
1 Schmidt. Mem. Acad. imp. sci. St. Petersb., 1881, ser. 7, 30, no. 1, p. 49. 
