THE BRYOZOAN FAUNA OF THE 
ROCHESTER SHALE." 
By Ray S. Bassler. 
INTRODUCTION. 
As compared with the other Paleozoic systems affording bryozoa, the Silurian, with the 
exception of the Helderbergian b group, has received least attention. Ulrich has elucidated 
the bryozoa of the Ordovician and Carboniferous systems particularly in several important 
monographs, while Hall and Simpson have summed up their papers on this class in Volume 
VI of the Paleontology of New York, where they have given a comprehensive idea of the 
many beautiful forms found in the Devonian. However, it can not be said that the bryozoa 
of any of the Silurian formations have been totally neglected, as a number of publications 
touch on them. Still, few authors have attempted to work out a fauna in detail. As 
early as 1852 Professor Hall published fairly complete accounts of the faunas of the Clinton 
and Niagara of New York, and in 1876 he gave descriptions and figures of the fine assem- 
blage of species found at the noted Niagaran locality, Waldron, Ind. The bryozoa, as well 
as the other classes, were well represented in these faunas, but, on account of the inadequate 
methods then used in discriminating specific and generic types, Professor Hall's work needs 
revision. 
Instead of reviewing the Silurian faunas in their geologic order, a study of the species of 
the Rochester shale has been undertaken first, because the most complete collections that 
the writer has had the opportunity of studying are from this formation. Since the number 
of species here is also apparently larger than in any other Silurian horizon, this paper can 
be used as the basis for comparative remarks in future articles. 
Through the kindness of Mr. B. E. Walker, of Toronto, Canada, the writer has been 
enabled to study the collection made in the vicinity of Grimsby, Ontario, by the late Mr. 
Pettit. This is a most excellent collection of fossils from the Rochester shale and contains 
several of the types figured in this paper. A fine collection from Rochester, N. Y., was 
loaned by Mr. Z. F. Westervelt. Mr. Clifton J. Sarle presented a good series of bryozoa 
from the same region. Dr. A. W. Grabau loaned all of the material collected by him during 
his study of the Niagara region. Prof. R. P. Whitfield loaned the Hall types in the Ameri- 
can Museum of Natural History. Prof. J. F. Whiteaves sent many Canadian specimens 
for examination. To all these gentlemen the writer wishes to express his obligations for 
their generous help. The paleontologic collections of the United States National Museum 
are rich in Niagara bryozoa and contain, with a few exceptions, all of the material described 
and figured here. These collections were made at various times by Mr. G. T. McComb, of 
Lockport, N. Y.; Messrs. E. O. Ulrich, H. E. Dickhaut, and J. M. Nickles, of the United 
States Geological Survey; Prof. Charles Schuchert, of Yale University; and the writer. 
a Published by permission of the Assistant Secretary of the Smithsonian Institution. 
b Throughout this paper the group names used follow the New York classification recently proposed 
by Messrs. Clarke and Schuchert, although these terms have not been officially adopted by the 
United States Geological Survey. 
