!•• PALJSONTOLOGY OF NEW- YORK. 



The formations of this age, which have been identified in Canada as 

 far to the northeast as Gaspe, have not yet furnished determinable forms 

 of Crinoidea), though fragments of them are of common occurrence in the 

 strata. In the present state of our knowledge, however, it is impossible 

 to arrive at any general conclusions regarding the probable number and 

 distribution of the Crinoidea) and Cystideae of this period. 



We have heretofore regarded the Niagara period in America, as the 

 Wenlock period is in Great Britain, the most prolific in these forms of 

 fossil remains ; but we have more recently learned that a single locality 

 of Lower Silurian limestones in Canada has furnished more species of 

 Crinoideoe and CystideoB than have heretofore been found in all Lower 

 and Upper Silurian strata together. The known habits of these animals, 

 and the very limited geographical range of most of the species, are 

 sufficient to warn us against conclusions based upon, the very partial 

 explorations yet made in the strata of this period. 



The Oriskany sandstone, within the limits of the State of New- York, 

 has not furnished any well-defined species of Crinoideae or Cystideae j 

 but in tracing this rock to the southwest along the Appalachian chain, it 

 becomes developed in much greater degree than in New- York, and con- 

 tains numerous species of fossils not known in this State. Among these 

 are several species of crinoids, of genera similar to those of the limestoties 

 below; showing, by these fossils as well as by the Brachiopoda and 

 Gasteropoda, the intimate zoological relations of the two groups of strata. 



Among the peculiar forms which mark both the limestones and the 

 sandstone, the Edriocrinus is perhaps the most remarkable : a crinoid 

 which is sessile in its young state, and firmly attached to other bodies 

 by the base of its cup, but becomes free as it advances, and gradually 

 loses all evidence of a cicatrix ; the base becoming rounded and smooth, 

 or, very rarely, preserving a depression or pit near the centre, which 

 marks the original point of attachment. 



There is likewise another somewhat similar form with solid base, which 

 preserves the marks of attachment of the column ; but all the specimens, 

 thus far discovered, have afforded no clue to the structure of the upper 



»> 



