No. 189.] 51 



Among the Actinocrinus, we find an approach to some of the 

 species in the Burlington limestone ; and the same is true of one 

 species of Platycrinus, while the Forbesiocrinus hav^e analogues 

 in both the Burlington and Keokuk limestones of the Carboniferous 

 system. Two of the species of Scaphiocrinus bear a close simila- 

 rity to species of the Burlington limestone, and one of the Zea- 

 CRiNus is equally like a form in the same rock. 



Had the collection been investigated with the knowledge of 

 Crinoiuea possessed some two or three years since, we would 

 undoubtedly have referred them to Carboniferous equivalents ; 

 but the discovery of numerous species in the Hamilton group of 

 New-York has afforded data for comparison, of the highest in- 

 terest for the solution of the problem. Applying this knowledge, 

 therefore, to the Ohio collection, we find among the Actinocrinus 

 no species of a more carboniferous aspect than the A. precursor 

 of the Hamilton group. 



The most abundant species of this genus is of the type of Jl, 

 tenuis^ De Koninck ; A. icosidactylus, Portlcck, and A. costus, 

 M'CoY, of Europe, and the A. ornatus of the Burlington limestone ; 

 but we have in the Hamilton group the A. eucharis and A. calypso^ 

 which are equally carboniferous types. 



In the Forbesiocrinus, one species is undistinguishable from, 

 and apparently identical with, a species of the Hamilton group ; 

 while another, though allied to a known Carboniferous species, 

 is even more analogous to one in the Hamilton group, and the 

 most abundant species of the genus is allied in some respects to 

 species of the Keokuk limestone; but an individual of the same 

 species has been found in undoubted beds of the Chemung group 

 in New- York. 



The PoTERiocRiNus forms resemble some of those in the Hamil- 

 ton group, and one species is extremely similar. In the Scaphio- 

 crinus and Zeacrinus, we have the nearest analogues in the 

 Burlington limestone. 



Left to the evidence afforded alone by the collection, and the 

 means of comparison at present possessed, I should infer that the 

 geological position of these species is between the Hamilton group 

 and the lower carboniferous beds; while the occurrence of a single 

 species identical with one in the former group, and another iden- 

 tical with a species in the middle of the Chemung group, will 

 ally them more nearly with the fauna of the Hamilton group, 

 than with that of the Carboniferous period. 



