B1GSBY — PALEOZOIC BASIN OF NEW YORK. 



451 



carefully in a zoological point of view, the supposed identity of 

 species in different geological formations vanishes gradually more 

 and more." .... " Facts do not exhibit a gradual disappearance of a 

 limited number of species, and an equally gradual introduction of an 

 equally limited number of new ones, but, on the contrary, the simul- 

 taneous creation and the simultaneous destruction of entire faunae. " 

 In another place (p. 96), Agassiz observes, " There was, during each 

 great geological era, an assemblage of animals and plants differing 

 essentially for each period : and by 'period' I mean those minor 

 subdivisions in the successive sets of strata of rocks which consti- 

 tute the crust of our globe, the number of which is increasing daily, 

 as our investigations become more extensive and more precise." 



We may therefore conclude that the proximate extinction of the 

 fauna of the Hudson-River section does not necessarily announce the 

 advent of a new palaeozoic system. But, as was shown by a table in 

 the Synoptical View, more fossils survived the Oneida break than 

 has been generally supposed. 



List of New York Fossils which have escaped, past the Oneida Con- 

 glomerate, from the Lower to the Upper Silurian Stage. 



Fossils. 



Chaetetes Lycoperdon 



columnaris 



Stromatopora concentrica. 

 Glyptaster brachiatus 

 Hemicystites parasiticus .. 



Leptaena alternata 



depressa 



(Stroph.) grandis 



(Stroph.) sericea .... 



Atrypa reticularis 



Bellerophon bilobatus 



Calymene Blumenbachii .. 

 Platynotus Trentonensis . 



Phacops limulurus 



Orthoceras aequale 



*H 



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s 



o 



bC 

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rs 



o 



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H. signifies Hall as authority ; V, De Verneuil ; S, Daniel Sharpe ; C, Conrad; 

 E, Emmons. 



Of the fifteen escaped fossils, two are doubtful, but worth notice 

 — Hemicystites parasiticus (Trenton Limestone and Niagara Lime- 

 stone, Hall), Bucania trilobata (Utica Slate, Hudson River group, 

 Medina Sandstone, Hall). 



