NATURAL SCIENCES OF PHILADELPHIA. 335 



Eemarks on some types of Carboniferous CRINOIDEA, with descriptions of 

 new Genera and Species of the same, and of one ECHINOID. 



BY F. B. MEEK AND A. H. WORTHEN, 



Of the Illinois State Geological Survey. 



Since the publication of the second volume of the Illinois Geological Re- 

 ports, in 1866, other engagements have, until recently, prevented us from at- 

 tempting any further investigations of the Crinoidea, beyond the preparation of 

 some specific descriptions for the third volume. On several occasions we have ex- 

 pressed the opinion, that the classification of these animals, as entireli/'based upon 

 the number and arrangement of the pieces composing the walls of the body below 

 the arms, without regard to the most extrao?-dinan/ diSevences in other parts, is, 

 to a considerable extent, artificial ; and that when larger collections, containing 

 perfect specimens, showing the whole structure of a greater number of species 

 of various types could be obtained for study, considerable modifications in the 

 limits of genera, as most generally understood, would be found necessary. Im- 

 pressed with this opinion, we separated in the third vo'urae of the Illinois Geo- 

 logical Reports and elsewhere, either as distinct genera, subgenera, or less 

 important sections, various types that had already been named by difi'erent 

 parties in this country and Europe, as distinct genera, but which had been 

 almost entirely overlooked or neglected by most authors, while to a few other 

 types we gave, for the first time, distinct names. 



Having recently had an opportunity to study in Mr. Wachsmuth's collection 

 at Burlington, Iowa, what we really believe to be by far the most extensive 

 collection of finely preserved Carboniferous Crinoids ever brought together, 

 either in this country or Europe, we have been more than ever impressed, not 

 only with the importance of the separations we had previously admitted, but 

 with the necessity for giving even greater prominence to some of those groups 

 than we have hitherto done, as well as for making other divisions. It is only 

 when we can study a great collection like this, in which specimens may be count- 

 ed by hundreds, showing the whole structure of numerous species belonging 

 to various genera, that it can be fully realized how readily we may arrange 

 them into perfectly natural groups, distinguished in part by other characters 

 as well as by the structure of the body. In addition to this, in attempting to 

 classify such a collection as this by taking into consideration the structure of 

 the body o/ily, we soon find that we would often have to include in a single genus 

 forms ditfering very widely, on as important other characters, as those distin- 

 guishing many of the universally admitted genera of other groups oi' Echino- 

 dermata. 



When once we have become familiar with the different groups, as separated 

 by a careful study of the entire structure of these animals, it is surprising to 

 see how readily' we may generally separate them, even from very imperfect 

 specimens, upon some seemingly unimportant characters scarcely ever noticed 

 by those who give the widest limits to genera. That such divisions greatly 

 facilitate the study of these fossils must also be evident to any one who will 

 attempt to identify the numerous species of some allied groups contained in a 

 large collection. 



With regard to the new species described in this paper, as well as others 

 that we expect to describe hereafter from the same horizon, it may be proper 

 to state, that we have had the advantage of being able to compare them direct- 

 ly (assisted by Mr. Wachsmuth) with authentic specimens of very nearly all 

 the described species from the Burlington rocks. Many of the original typical 

 specimens we have here at hand in Springfield, while Mr. Wachsmuth has in his 

 own collection good specimens of nearly all the described Burlington species. 

 Many of his specimens are also types of species, while most of those that are 

 not, have been identified from direct comparison by him and Mr. Niles and our- 



1868.] 



