464 GEOLOGY OF OHIO. 



The individual specimens are much too few in number to give any 

 very satisfactory idea of the general form of the complete body, or of 

 the number of ranges of plates of which it may have been composed. 

 There appears to be no reason however, to doubt the correctness of the 

 reference of these plates to the genus Plumulites Barrande, as their gen- 

 eral form and surface structure are exactly like thoss given by Dr. 

 Barrande, and also to those given in Vol. II, Pal. Ohio, pi. 4, figs. 1 and 

 2 (P. Jamesi), as occurring in the rocks of the Hudson river group, at 

 Cincinnati; while some idea may be obtained of the probable form of 

 the entire body from the outline figure of a European species, repre- 

 sented in fig. 3 of the same plate. These Devonian specimens, however, 

 have been of very much greater size than the above, as the plates here 

 figured are all represented of natural size, the larger individual plates 

 being more than an inch in transverse diameter, while the species above 

 referred to is minute. The occurrence of forms of this genus in rocks 

 of Devonian age is also a new feature in its history; as those of Europe 

 are confined to the Lower Silurian formations and the lower beds of the 

 Upper Silurian; while these occur above the middle Devonian. 



Formation and Locality. — In the Cleveland shale at Sheffield and 

 Birmingham, Erie county, Ohio. 



