INTRODUCTION 
9 
Origin of the Work 
The idea of a systematic work upon the American Silurian crinoids was 
first suggested by the account of the wonderful crinoidal fauna of Gotland by 
Angelin in his Iconographia Crinoideorum, and afterward by Bather in the Cri- 
noidea of Gotland, and by my observations upon the English collections from 
the Dudley area above mentioned. The collections made by Wachsmuth in Ten- 
nessee and Beachler in Indiana indicated a certain correspondence between the 
Silurian crinoidal faunas of the two continents which offered an inviting subject 
for investigation, and it was probably this consideration which induced the be- 
ginning of efforts toward the assembling of material with reference to it. It was 
not until the discovery of the rich collections made by Pate in 1906-7 that the 
plans took definite shape with the starting of drawings by Mr. Chapman, con- 
current with the work upon the Flexibilia. These were prosecuted from time to 
time in a desultory way, as the demands of business and of other work permitted, 
and were continued as additional material was acquired. Preliminary studies 
and notes were made in the same irregular way, but it was only in 1923 that I 
found myself in a position to assemble the drawings, and begin the final prepa- 
ration of the text. 
At this point the work was suspended by a protracted physical breakdown 
incident to an impaired heart, from which a slow recovery has enabled me to 
resume it at intervals. That I have been able to bring the work to a conclusion 
is a result that was not expected; and for which I am profoundly thankful. 
In conformity with the preparatory field-work, this treatise is chiefly limited 
to the Silurian faunas of Tennessee and Indiana. The crinoids of the Lockport 
field have been thoroughly treated by Plall and Ringueberg, and a few of them 
since by myself. Weller’s and Slocom’s works upon the Chicago crinoids cover 
that field exhaustively. Therefore, except for incidental reference to a few 
forms for special reasons, it has not been deemed necessary to include those of 
either field. For a similar reason I am omitting most of the Waldron species, 
which were so fully described by PTall. 
The effort is made to reduce the treatment of species to a simple presenta- 
tion of the essential facts, avoiding so far as possible the formal recital of char- 
acters which often becomes irksome. In some instances, where a form or group 
has been the subject of extended discussion hitherto, or where the acquisition 
of new material has thrown important light upon forms or questions before 
obscure, full latitude is employed. This will account for some differences in 
method that may be noticeable. 
In the descriptions it has not been thought necessary to include tables of 
dimensions. They are usually only a pedantic incumbrance, inasmuch as the 
same information is more conveniently furnished by the drawings, which are 
