346 PALAEONTOLOGY OP ILLINOIS. 



BLASTOIDS, 



WITH OBSERVATIONS UPON 



THE STEUCTUEE OF THE BASAL PLATES IN CODASTEE 

 AND PENTEEMITES. 



Among some interesting new Blastoids, lately sent to me for in- 

 vestigation by Eev. W. H. Barris, of Davenport, Iowa, collected by 

 him in Northern Michigan, I found one type, which seemed to me 

 of unusual interest as representing a form intermediate between 

 Cadaster. McCoy, and the new genus Phcenoschisma, Ether, and Carp. 

 At my request, Mr. Barris not only kindly permitted me to describe 

 the species, but he very liberally furnished me a number of speci- 

 mens, which he allowed to be cut for sections. Before giving the 

 description of the form, I wish to make a few remarks upon the 

 terminology employed in this and the succeeding paper by Mr. Barris. 



Since the appearance of Prof. F. Eoemer's classical work upon 

 the Blastoidea, his terms, with slight variations, were used, both in 

 this country and in Europe, by all the leading palaeontologists. 

 Eoemer's terms are no doubt appropriate, but they have the great 

 disadvantage of giving new names to certain parts which in allied 

 groups had previously received a proper designation. All parts that 

 are founded upon identity of plan, or which are analogous in their 

 functions, should always be called by the same name. Special 

 terms, unnecessarily introduced, lead to the impression that the 

 differences among the groups are greater than they really are, and 

 they form a serious obstacle to an easy perusal of the works of dif- 

 ferent writers. 



