PRELIMINARY OBSERVATIONS. Y/ 
I have also to acknowledge much valuable assistance from my Scottish friends, 
who have spared no trouble while assembling for my use all that their collections and 
localities would afford. From Messrs. J. Thompson, J. Young, J. Armstrong, and Mr. 
and Mrs. Gray, of Glasgow, I have received a large number of Ayrshire Silurian 
specimens. ‘The Pentland Silurian series has been kindly contributed by Messrs. G. C. 
Haswell, D. J. Brown, and J. Henderson, of Edinburgh; and I am, moreover, indebted to 
Mr. A. Geikie and Dr. Young, of the Geological Survey of Great Britain, for much 
valuable information with reference to Scottish Silurian geology and localities; and 
from Mr. Slimon, of Lesmahago, I have received useful information and the Silurian 
species of his district. 
From Ireland I have also been able to study a large number of Silurian species ; and 
my thanks are particularly due to Mr. J. B. Jukes, Director of the Geological Survey of 
Ireland, as well as to Mr. W. H. Baily, Paleeontologist of the same Survey, for the kmd manner 
with which they forwarded to Brighton, for my inspection and study, the large and very 
valuable series of Silurian Brachiopoda that has been collected during the Geological 
Survey of Ireland; and I have also to thank Sir R. Griffith, Bart., and Mr. R. Byron, 
for the loan of the original series of Silurian Brachiopoda described and figured by Prof. 
M‘Coy in his ‘Synopsis of the Silurian Fossils of Ireland.’ I am likewise indebted to 
Mr. J. Wright, of Cork, for many specimens obtained at the Chair of Kildare and 
other Irish localities. 
My thanks are likewise due to Mr. E. de Verneuil, Prof. L. de Koninck, Dr. Volborth, 
M. Barrande, Prof. F. Roemer, Herr G. Lindstrém, Herr F. Schmidt, Capt. V. de Moller, 
Prof. Hall, Mr. Billings, Sigr. Meneghini, and to several other friends, for much valuable 
information in connection with foreign Silurian species. 
I may, in conclusion, here remark that, besides the very large number of original 
illustrations that will be found in this Monograph, I have, wherever such appeared desir- 
able, reproduced the original figures, as well as part of the descriptions, published by the 
first describer of the species, so that no doubt may exist with reference to the identifica- 
tion. 
