RAYMOND: CORREL-^TION OF THE ORDOVICIAX STRAT.a. 265 



Brachiopoda. 



The Brachiopoda are listed by Lamansky under twelve generic 

 names, but here comparisons are less satisfactory as the species have 

 not been studied critically. Orthis as used in this list includes Orthis 

 s. s., and Dalmanella, and should include Platystrophia, two species of 

 which occur, but are not listed by Lamansky. Acritis should also be 

 added. This increases the list to fifteen genera, two of which we may 

 at once drop, Leptaena as being meaningless in the present state of 

 our knowledge of the three species referred to it, and Lingula as being 

 cosmopolitan. Of the thirteen genera then remaining, eight, Poram- 

 bonites, Lycophoria, Plectella, Pseudocrania, Acritis, Pseudometop- 

 toma, Philhedra, and Siphondtreta, are unknown in the Ordovician 

 of America. Orthis is known from the American Beekmantown, 

 Dalmanella is probably there, though doubts have been cast on some 

 of the species so referred, and Strophomena may be there, but the 

 reported cases are questioned. Clitambonites appears first in the 

 Chazy, and Platystrophia in the Trenton. In passing, it may be said 

 that Orthis obtusa Pander, which is very abundant, belongs to an un- 

 described genus, unknown in America, and that Orthis parva Pander, 

 which Wysogorski (57) states can not be a Dalmanella because im- 

 punctate, is in reality exceedingly punctate. Orthis is very common 

 and exceedingly variable in these deposits, but all the species agree 

 in having a much lower cardinal area and a much wider delth\Tium 

 than the species which we in America know as a t^-pical Orthis (p. ex. 

 Orthis tricenaria). Orthis panderiana Hall and Clarke, of our Beek- 

 mantown, is much more like the typical Orthis of the ^Yalchow. 



Bryozoans. 



As pre\-iously stated, Bassler describes twenty-six species and 

 varieties from these two formations, four species and one variety being 

 identified as common to Russian and American deposits. Arthro- 

 clema armatum is said to be common to the ^Yalchow and to the 

 Xematopora and Fusispira beds of Minnesota (Upper Trenton). 

 Dianulites petropolitanus, which in Russia ranges from the \Yalchow to 

 the Wesenberg, is also identified in the same upper Trenton strata in 

 Minnesota. Batostoma fertile and its variety circidare are said to be 

 common to the Kunda formation of Russia and the Stictoporella bed 

 (Black River) of Minnesota. Hemiphragma irrasum, found in the 



