viii PKEFACE. 



to be expected that there should be a complete concordance of opinion between 

 workers who approach the subject from altogether different sides ; and the discovery 

 of the truth, which is the ultimate object of us all, can only be attained by a com- 

 bined investigation along several converging lines of inquiry. 



Besides providing us with material, Mr. Wachsmuth has also been kind enough to 

 keep us informed from time to time of the progress of his own researches, and in some 

 instances these have led to the abandonment or modification of views which we had 

 previously expressed. Thus, for example, we did not become fully aware until the 

 end of last year that the Silurian Troostocrinus Beinwardti must be separated generi- 

 cally from most of the Carboniferous species usually referred to this genus ; and it 

 was not till March last that we learnt of Mr. Wachsmuth 's most important discovery 

 that Stephanocrinus is not a Blastoid at all, but a Brachiate Crinoid. The earlier 

 sheets of this work, therefore, contain many passages which would have been dif- 

 ferently expressed had we known as much when they were written as we do now. 

 But we are indebted to Mr. Wachsmuth's kindness for the opportunity of modifying 

 our earlier statements in the later portion of the Catalogue, and we can now 

 only tender him our most sincere thanks for the very free use which he has allowed 

 us to make of his unpublished observations. (See pp. 118, 196.) 



We have also to express our gratitude to the many other scientific friends, both at 

 home and abroad, for the ready way in which they have facilitated our work, either 

 by the gift, exchange, or loan of specimens, or by valuable information of various 

 kinds. We would mention especially Professor W. H. Barris, of Davenport, Iowa ; 

 Mr. R. R. Rowley, of Curryville, Missouri ; Professor A. H. Worthen, of Springfield, 

 Illinois ; Messrs. S. A. Miller and A. G. Wetherby, of Cincinnati ; and Mr. E. N. S. 

 Ringueberg, of Lockport. Don Lucas Mallada, of Madrid ; Professors L. G. de 

 Koninck and G. Dewalque, of Liege ; Prof. F. Roemer, of Breslau ; M. Munier- 

 Chalmas of Lille ; and Professors Albert Gaudry and E. Perrier, of Paris, have all 

 been kind enough to supply us with valuable material ; and we have been similarly 

 favoured nearer home by Dr. A. Geikie, Director-General of the Geological Survey 

 of Great Britain; Mr. J. Bennie, of Edinburgh; Prof. H. A. Nicholson, of Aber- 

 deen ; Prof. T. McKenny Hughes, of Cambridge ; Prof. W. J. Sollas and Mr. W. H. 

 Baily, of Dublin ; Prof. W. Boyd Dawkins, of Manchester ; Dr. G. J. Hinde, of 

 Mitcham ; Rev. G. Style, of Giggleswick ; Rev. G. F. Whidborne, of Torquay ; and 

 Mr. !). Geddes, of Blackburn. All these gentlemen have responded to our inquiries 

 with the most liberal kindness, and we therefore take this opportunity of expressing 

 our thanks to them for their help. 



The material lent us by these gentlemen and from other sources has fur- 

 nished 89 figures, in addition to the 72 figures drawn from Mr. Wachsmuth's 

 collection ; while 178 specimens illustrated by 245 figures are in the National 

 Collection. The latter contains representatives of all the nineteen genera of 



