362 



PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



the rocks below the Oriskany Sandstone (Hall). Although in the 

 Niagara of America (= Wenlock) we have the family Cyathophyl- 

 lidse represented by Streptelesma caninia and three new genera 

 here introduced, we have no true Cyathophyllum, nor have we Cysti- 

 phyllum nor Heliophyllum at the same period (Hall, Pal. ii.). 



Fossils typical. — The number of fossils peculiar to this group is 

 very great ; in part because they belonged principally to animals not 

 migratory, and often fixed to a rocky bottom, such as the Echino- 

 dermata, Zoophyta, Bryozoa, and others. 



All the Bryozoa are typical except two ; so are thirty-two Zoophyta 

 out of thirty-seven ; and twenty-five out of twenty-six Echinoderms. 

 So also are all the Crustacea ; and, save one, all the Cephalopoda. 



This remarkable independence of other groups as to animal life 

 must have arisen from certain conditions of matrix, depth, and tem- 

 perature, which in the New York basin underwent a violent and 

 sudden change by the advent of the variable sands of the Onondaga- 

 Salt group, often charged with muriatic and sulphuric acids. 



Fossils occurrent in Europe. — Sir R. Murchison states that this 

 group contains more European fossils than all Lower Siluria. 



Forty- seven European fossils occur in the Niagara group alone. 

 Of these, one (France) is Lower Silurian ; one Mid-Silurian (Upper 

 Caradoc) ; six belong to Wenlock Shale ; twenty-one to Wenlock 

 Limestone ; three to the Devonian series : of fourteen, the exact place 

 I cannot ascertain, but most of them wear the Wenlock facies. They 

 must be Upper Silurian, together with one or two more not men- 

 tioned. (See Table V.) 



Forty-seven European fossils out of 180 (just one quarter) is a 

 great number, and especially when we consider that ninety-six of these 

 New York fossils are new species, unknown elsewhere. Twenty-nine 

 are Brachiopoda. 



This state of palaeozoic life, combined with a close agreement in 

 lithology, almost identifies the Niagara group with the Wenlock of 

 England and Sweden. 



Fossils recurrent in New York. — This group possesses thirty-eight 

 recurrents, the life-links which connect it with the other parts of the 

 system. Of these, nineteen come only from the Clinton ; six from 

 the lower Silurian ; seven originate in the Niagara and pass upwards ; 

 and only four use it as a passage into the newer deposits. These are 

 Catenipora escharoides, Stromatopora concentrica, Leptcena depressa 

 and Atrypa reticularis. (See Table IX. in Appendix). 



Coralline Limestone of Schoharie. 



Mineral Character. — This is in reality a mere continuation of the 

 Niagara group of the western limits of New York. See above, p. 360. 

 It scarcely required separation. 



It is a dark limestone, with a varying proportion of argillaceous 

 matter, and received its name from the immense number of corals 

 (chiefly Favosites) it contains. 



Transition. — This takes place gradually, both vertically and hori- 

 zontally. 



