PEEEACE. 



The following Decade contains descriptions of all the Crinoirls of 

 the Lower Silurian rocks of Canada, of which specimens have been 

 procured in such a state of preservation as to admit of their being 

 characterized. Of these, five belong to the Chazy limestone, and 

 the remainder to the Birdseye, Black River, Trenton, and Hudson 

 River formations. Altogether we have about fifty species, including 

 several which have been as yet recognized by their columns only. 



Of the thirteen genera to which I have referred these species 

 two, Rhodocrhms (Miller,) and Glyptocrimis (Hall), occur in the 

 Silurian rocks of Europe, but none of the species are common to 

 both sides of the Atlantic. Five of the genera, Heterocrinus, 

 Glyptocrimis, Dendrocrinus, Lecanocrinus, and Rhodocrinus, have been 

 found in the State of New York, the first two in the Lower Silurian 

 and the last three in the Upper Silurian. None of the other eight 

 genera have been noticed as occurring out of Canada, although it is 

 highly probable that some, if not all of them, will, in course of time, 

 be discovered in the Silurian rocks of the adjacent countries. 



The most remarkable species is the one to which we have given 

 the name of Blastoidocrinus carchariesdens. This fossil, by the 

 structure of its ventral surface, is closely allied to Pentremites, the 

 typical genus of the order Blastoideae, while the arrangement of the 

 plates in the walls of the lower part of the body, so far as it can 

 be made out from the imperfect specimens that have been collected, 

 seems to connect it with the Crinoidese. The species is interesting, 

 as it shews us that the organization peculiar to the Blastoideae, 



