eal PabeAGCa le 7 
In a collection of fossils obtained by Dr. Cooper Curtice in the Coosa 
Valley of Alabama during the summer of 1886 there were a number of 
siliceous nodules embedding fragments of trilobites and brachiopods of the 
Middle Cambrian fauna. A few had a radiate-lobed appearance that sug- 
gested the sea-urchin, while a few others had what appeared to be a star- 
fish flattened out on the nodule. Large collections were subsequently made 
by a local collector, Mr. Henry Bufford, but it was not until 1893 that I 
felt sure that the so-called ‘‘ star-cobbles” contained fossil medus:e.. When 
I came to the conclusion that this was the case, I began an investigation of 
the subject, but owing to pressure of administrative duties, the work was 
frequently interrupted. It was continued, however, in a desultory way 
until the winter of 1895, when it was pushed to completion. In the course 
of the investigation I found it necessary to make comparisons with other 
fossil forms, and having assembled material from the Cambrian strata of 
Sweden and the Jurassic of Bavaria, I decided to enlarge the scope of tie 
work so as to embrace all fossil medusze. 
In the course of my investigations I frequently consulted with Prof. 
W. K. Brooks, of Johns Hopkins University, Baltimore, Maryland, and am 
indebted to him for references to rare publications relating to the subject 
of the medusze. The assembling of the literature pertaining to the Jurassic 
meduse was the work of Mr. George H. Girty, of the United States Geo- 
logical Survey; and Mr. Charles Schuchert, of the United States National 
Museum, aided me in securing material from the Jurassic of Europe. In 
the endeavor to obtain evidence of the presence of fossil medusve at different 
geologic horizons in Europe, I corresponded with and received assistance 
from Dr. H. B. Geinitz, of Dresden, and Dr. Wilhelm Pabst, of Gotha, 
Saxony; Dr. Karl Zittel and Dr. J. F. Pompeckj, of Munich, Bavaria; Dr. 
H. Pohlig, of Bonn, Germany; and Dr. F. A. Bather, of London, England. 
ix 
