36 



BULLETIN 77, UNITED STATES NATIONAL MUSEUM. 



make it certain that some part of this group is represented in the 

 section. Many of the specimens of these particular species show a 

 shght difference in color and preservation from the Trenton forms 

 discussed above. The more recent study of this Baffin Land fauna 

 disclosed the presence of at least six species of Bryozoa, so that the 

 remarks above concerning the practical absence of these forms are 

 less to the point. Indeed, it is believed that the bryozoans are 

 present, but because of their uninteresting aspect to the usual student, 

 were not collected. 



Summing up, it seems probable from Schuchert's results, combined 

 with the more detailed correlations of the present paper, that the 

 geologic section at Baffin Land consists of Black River strata resting 

 upon the old crystalline rocks, followed by an early Trenton forma- 

 tion equivalent to the Stewartville and Prosser limestones of Minne- 

 sota, and this in turn succeeded unconformably by the widespread 

 coral zone of the Richmond group. The same succession of strata, 

 so far as the Trenton and Richmond divisions are concerned, is present 

 on Akpatok Island, near the south shore of Hudson Strait, where the 

 species hsted below were collected. Those marked with an asterisk 

 are characteristic Richmond forms, while the remauiing refer to 

 Trenton and possibly Black River species : 



Receptaculites oweni Hall. 

 ^Streptelasma robustinn Whiteaves. 

 *Calapcecia canadensis Billings. 

 *Rafinesquina lata T\Tiiteaves. 

 *Leptxna unicostata (Meek and Worthen) . 

 Plectambonites sericea (Sowerby). 

 Orthis tricenaria Conrad. 



Orthis (Dinorthis) meedsi arctica Schuchert. 

 Orthis (Hebertella) bellirugosa (Conrad). 

 Orthis (Dalmanella) testudinaria (Dalman). 

 Platystrophia biforata (Schlotlieim) . 

 IRhynchotrema inequivalvis (Castelnau). 

 Cyrtoceras manitobense "^Tiiteaves. 



STRATIGRAPHIC CORRELATIONS. 



The exact position within the Ordovician system of the Russian 

 formations under discussion can be determ^ined only by comparison 

 with sections in other parts of the world. The Baltic section has rather 

 generally been regarded, especially by European geologists, as an 

 excellent illustration of contmuous sedimentation from some time 

 in the Cambrian on weU into the Silurian. The error of this view 

 must be apparent to all who will compare the Baltic sequence with 

 the much greater development of corresponding parts of the geo- 

 logical column in America. The exceeding inadequacy of the Baltic 

 section as the type for the Eopaleozoic is graphically shown in the 

 accompanying correlation table. 



In the foregoing pages I have attempted to show (1) that, judging 

 from the bryozoan faunas, the strata ranging from the Glauconite 

 sandstone to the Wesenberg should be correlated with the American 

 Black River; (2) that the Wesenberg and early Lyckholm show 



