374 REVIEWS 
remains of apparent Pottsville age in beds subjacent to the Caney shale. 
The final correlation of the Mississippian faunas of northwestern Arkan- 
sas and Oklahoma must rest until much more investigation upon them 
has been completed. 
S. W. 
The Early Paleozoic Bryozoa of the Baltic Provinces. By Ray S. 
BassteER. U.S. National Museum Bulletin 77. 
In this paper the stratigraphy of the Ordovician and the lower part 
of the Silurian rocks of the Baltic provinces is considered briefly and the 
bryozoan fauna is described and figured. Complete faunal lists of the 
formations are also given. 
The Paleozoic rocks of this region have usually been considered as 
representing a complete section of the Cambrian, Ordovician, and 
Silurian systems, with the exception of the Middle Cambrian. The 
bryozoan faunas indicate, however, that instead of the whole of the 
Ordovician being present only the Beekmantown (Canadian of Ulrich), 
the Black River (of Ulrich), and the earliest Trenton are represented. 
The Lyckholm and Bornholm beds, which have been hitherto corre- 
‘lated with the Utica, are believed to be of Richmond age and are placed 
at the base of the Silurian. 
For the purpose of comparison, the stratigraphy of the Upper Missis- 
sippi Valley region is reviewed and the bryozoan faunas of these forma- 
tions are considered briefly. Reference is made to the strata and 
faunas of the same age in Arctic America. From the comparison of the 
faunas, it is decided that the faunas of the Ordovician and the early 
Silurian of the Baltic provinces and of central and northern America 
were derived from the Arctic region. The resemblance between the 
faunal elements requiring shore-line conditions for migration is strong 
but not nearly so marked as in the types not dependent on these condi- 
tions. The resemblance is especially marked in the case of the bryozoa, 
for out of the 237 species found in the Ordovician and Richmond beds of 
the Baltic region, 86, or over one-third, are also known from America, 
and many others are closely allied forms. 
The greater portion of the bulletin is taken up with the description 
of some 200 species of bryozoa. The figures for each species are inserted 
in the text, and this should prove a great advantage over the usual 
method of separating the description and the figures. The figures, 
although printed on rather soft paper, are, with few exceptions, very 
clear, and there should be no trouble in using them for identification. 
