2 BULLETIN 77, UNITED STATES NATIONAL MUSEUM. 



vician formations on the island of Oeland, in the Baltic Sea, These 

 contained faunas so intimately related to those of the Russian prov- 

 inces that I have incorporated the results of their study. In addi- 

 tion I have presented an account of the stratigraphy and detailed 

 listaf of species of both the Baltic area and the American region which 

 the Russian faunas and formations most closely resemble. The 

 study of these bryozoan faunas has indicated that the greater part 

 of the Russian Ordovician section may be directly correlated with 

 the Black River group of America, while the Upper Lyckholm and 

 Borkhohn limestones are the equivalents of the Richmond group. 



Recent studies based upon paleontologic and diastrophic criteria 

 have indicated that the Richmond group of America, with its equiva- 

 lent in Baltic Russia, the upper part of the Lyckholm and the Bork- 

 holm limestones, should be classed as earliest SUurian. The bryozoan 

 faunas of these several formations afford ample evidence of this fact, 

 thus making it advisable to add their description and discussion to 

 the present work. 



Summing upj the paleontologic portion of this paper includes the 

 description of a single Cambrian bryozoan, of numerous Ordovician 

 species from the Baltic provinces of Russia and Sweden, and, finally, 

 of the faunas of the early Silurian, the Upper Lyckholm and the 

 Borkhohn limestones. 



Li the course of a general study of the West-European Paleozoic 

 rocks in the summer of 1903, Prof. Charles Schuchert, at my 

 request, gathered as many Bryozoa as possible from the Ordo- 

 vician rocks outcropping in the shore region of Esthonia, Russia, 

 between St. Petersburg and Reval. He was fortunate in hav- 

 ing as companions during this trip Prof. Friedrich von Schmidt, 

 and Dr. August von Mickwitz, whose authoritative knowledge of the 

 geology and paleontology of the region made these collections of 

 unusual value for stratigraphic purposes. Later, through Prof. 

 Schuchert, these collections were increased by the generous gift to 

 the United States National Museum, from Dr. Mickwitz, of his fine 

 lot of Russian Ordovician Bryozoa, this gift being made upon the 

 conditions that the collection be studied and a named set 

 be returned to the donor. Prof. George MikhaUowski, director 

 of the University Museum at Dorpat, was also kind enough 

 to loan collections of these fossils in his museum, which were of 

 especial value since they had been studied and labeled by Dybowski. 

 I am also indebted to Dr. F. A. Bather, of the British Museum, for 

 the loan of the bryozoan material collected by him from several of 

 the Swedish formations on the island of Oeland. In this way a con- 

 siderable amount of material was at my disposal for study, and a 

 detailed comparison of these various bryozoan faunas with those from 



II 



