8 
SMITHSONIAN INSTITUTEON 
The Chicago Area 
Another important Silurian area to be considered by way of comparison 
is that of the Racine dolomite at Chicago, which has produced a considerable 
crinoidal fauna, heretofore fully worked up and described by Stuart Weller ^ 
and A. W. Slocom." In this formation the calcareous test of the crinoids has 
been largely dissolved by chemical action, so that for the most part only the inter- 
nal casts are preserved. For this reason close comparison of characters is usually 
difScult. But the general facies of the fauna is very important, differing in many 
respects from those of southern Indiana and Tennessee, and paralleling that of 
the European Silurian in the presence of the highly specialized genus Crotalo- 
crinus. In this it is reinforced by the occurrence in the equivalent Hopkinton 
dolomite of Iowa of the equally specialized Petalocrinus, also of Gotland. 
The Foreign Silurian 
In view of the close parallelism between the American Silurian and that 
of northern Europe before alluded to, it became desirable to secure an adequate 
representation of the crinoids from the two principal localities, Dudley in Eng- 
land, and the island of Gotland, Sweden. I had the advantage during a sojourn 
in Europe in 1887 of personal examination and study of the great Silurian col- 
lections in the British Museum, and in the Dudley Museum, and also of several 
private collections at Dudley during a visit to that field, especially those of 
Mr. Charles Holcroft, now in the Birmingham Museum, of Mr. John Gray, 
since acquired by the British Museum, and of Mr. William Madely. Through 
the good offices of Messrs. Holcroft and Madely, and from other local collectors, 
I was able to secure considerable useful material from that famous locality, 
which has been increased by purchases and exchanges since. From Gotland the 
more common species were obtained from time to time from dealers, and rarer 
ones from the Riks Museum at Stockholm by exchange, thanks to the liberality 
of my good friend Prof. G. Lindstrom. In more recent years I secured the ser- 
vices of local collectors on the island, first of Prof. G. Klinteberg, and after- 
wards of Mr. A. Florin, an experienced collector, who knew the geology of the 
island thoroughly, whom I engaged for a season’s operations with blasting equip- 
ment. This resulted in some valuable acquisitions in the way of rare, and even 
new, forms, which have aided materially in the comparative study of the faunas. 
All of the material thus accumulated forms part of my personal collection 
in the United States National Museum, where it will remain in perpetuity. 
The total number of species herein illustrated and discussed is 198 belong- 
ing to 63 genera; of these 74 species are new and 12 undetermined. They are 
distributed as follows: Camerata, total 103, new 43, undetermined 12; Flexi- 
bilia, total 18, new 3 ; Inadunata, total 77, new 28. 
1 Bull. Chicago Acad. Sci., 4, pt. i, 1900. 
2 Field Columbian Museum, 2 , Geol. Ser., No. 10, 1908 
