RAYMOND: CORRELATION OF THE ORDOVICIAN STRATA. 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 Siphonotreta, 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 delthyrium 
than the species which we in America know as a typical Orthis (p. ex. 
Orthis tricenaria). Orthis panderiana Hall and Clarke, of our Beek- 
mantown, is much more like the typical Orthis of the Walchow. 
Bryozoans. 
As previously 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 Walchow and to the 
Nematopora and Fusispira beds of Minnesota (Upper Trenton). 
Dianulites petropolitanus, which in Russia ranges from the Walchow to 
the Wesenberg, is also identified in the same upper Trenton strata in 
Minnesota. Batostoma fertile and its variety circulare are said to be 
common to the Kunda formation of Russia and the Stictoporella bed 
(Black River) of Minnesota. Hemiphragma irrasum, found in the 
