76 DAVENPORT ACADEMY OF NATURAL SCTENCKS. 



ON A NEW GENUS AND SPECIES OF 

 BLASTOIDS, 



With Observations upon the Structure of the Basal Plates in 

 Codaster and Pentremites. 



BY CHARLES WACHSMUTH. 



[This article, which appeared in the Geological Report of Illinois, Vol. VII., 

 p. 346, has been revised by the author.] 



Among some interesting new Blastoids lately sent to me for investi- 

 gation by Rev. 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 Codaster McCoy 

 and the new genus Phmioschisma 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 specimens, 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. Roemer's classical work ui)on the 

 Blastoidea, his terms, with shght variations, were used, both in this 

 country and in Europe, by the leading ])ahcontologists. Roemer's 

 terms are no doubt approj^riate, but they have the great disadvantage 

 of giving new names to certain parts, which, in allied groups, had previ- 

 ously received a juoper designation. ^ All parts having a common 

 origin should always be called by the same name. Special terms, un- 

 necessarily introduced, lead to the impression that the difterences 

 among the groups are greater than they really are, and they form a 

 serious obstacle to an easy perusal of the works of different writers. 



Messrs. Etheridge and Carpenter have lately published, through the 

 Ann. and Mag. Nat. Hist., April, 1882, an interesting paper, "On cer- 

 tain points in the Morphology of the Blastoidea, with descriptions of 

 some new Genera and Species," in which they explain the terms which 

 they propose to use in their writings. Their terms are in conformity 

 with those now in use for Crinoids and other Echinoderms, and it 



