252 PROCEEDINGS OF THE ACADEMY OP [1879. 



In the discussion of the different genera, we shall give with each 

 a full list of the species which belong to it, in our opinion, inde- 

 pendent of the opinion of others, and this will cause many changes 

 in the reference of species. It cannot be expected that these lists 

 will be free from mistakes, though we have studied each species 

 with great care, the majority of them from the specimens, and be- 

 sides our own extensive collections, one of us had occasion a few 

 years ago to examine the original collections of De Konnick and 

 Schultze, now in theMuseum of Comparative Zoology at Cambridge. 

 Nor can it be expected that iu a general work on Crinoids like this, 

 we shall give a full list of synonyms, and we have not attempted 

 to do so. This can only be thoroughly done by the collector who 

 has given his attention for years to the fossils of his own locality, 

 and is able to identify them from the least fragment. We shall 

 give the synonyms of the subcarboniferous Crinoids of the Mis- 

 sissippi Valley which we have made our special study, and we 

 hope that investigators will do the same for other localities and 

 formations. We shall feel under special obligations to any of our 

 scientific friends for any information they may be able to furnish 

 us, either in the way of specimens or observations which may con- 

 tribute to a more thorough understanding and truthful presenta- 

 tion of the subject. We particularly desire this, as we intend to 

 embody the results of all our investigations in this field in a future 

 work to be issued with ample illustrations. 



We take this opportunity to tender our thanks to Prof. A. 

 Agassiz, of Cambridge; Prof. A. H. Worthen, of Illinois; Prof. 

 S. H. Calvin, of Iowa City; Prof. A. Gr. Wetherb}^, of Cincinnati; 

 Dr. James Knapp, of Louisville; Dr. Harrod, of Canton; Dr. K. 

 Zittel, of Munich; Dr. F. Roemer, of Breslau; and to Prof. Traut- 

 schold, of Moscow, Russ., for valuable assistance courteously ex- 

 tended to us in the loan of books or specimens. 



Note. Species founded upon mere fragments of column are not 

 recognized by us, and their names are enumerated only in the 

 list of s3 r noii3^ms and doubtful species. 



All species marked in front with an * are referred to said genus 

 for the first time. 



