BIGSBY PALAEOZOIC ROCKS OF NEW YORK. 357 



further west than the eastern border of Wayne County (Hall, 

 Pal. ii. 11). James Hall hesitates to consider them all Fucoids. 



The absence of coral in the east of this group is to be ascribed 

 to the nature of the sediment, and perhaps to agitation in the waters 

 that deposited it. 



Individual zoophytes abound in places, as from Wayne County 

 to the head of Lake Ontario ; and they resemble those of the Niagara 

 period. Here we find for the first time the Catenipora escharoides 

 (Halysites catenulatus), a world-wide fossil, together with the 

 Bryozoa Trematopora tubulosa and Retepora Clintoni (in iron-ore, 

 Vanuxem), and the new and beautiful Graptolites clintonensis and 

 G. venosus. The Crinoids of this group are only in moderate num- 

 ber. In its lower portions they are very rare, especially in Eastern 

 and Central New York, with the exception of some peculiar ring-like 

 bodies in the ore-beds of Herkimer County ; but, after passing to 

 the west of the Genesee River, the upper limestone is often wholly 

 composed of comminuted Crinoids (Hall, Pal. ii. 52). 



The eight species of Crinoids are, with one exception, of types 

 distinct from those of the Lower Silurian stage, and resemble more 

 those of the Upper Silurian. It is only the species of the Upper 

 Limestone that are Wenlock ; those below are distinct. 



Forty-three new Brachiopoda are here introduced, viz. five Lingulce, 

 seven Leptcence, five Orthides, three Spiriferi, eighteen Atrypce, and 

 three Pentameri. Individual Orthides are few, and the species are 

 fewer than in the lower stage. 



Only three Brachiopoda are derived from older centres of life, and 

 nine are transmitted onwards. Although very plentiful in the west, 

 Brachiopoda are rare east of Wayne County, where the habitats are 

 less suitable. 



The species most numerous in individuals are the little Atrypa 

 hemisphcerica and the A. congesta ; both of short vertical range. 



The Atrypce are more numerous now than the Leptence or Orthides, 

 and contrast in this respect with them strongly. Types come in 

 eminently significant of the middle or transition stage, or which assi- 

 milate with Upper Silurian species. In Atrypa we have the intro- 

 duction of the smooth, round, or sub-cylindrical forms, which scarcely 

 occurred in Lower Silurian. 



As we see from the Table No. IV., several Brachiopoda from the 

 Hudson-River-group come up here. It was once thought that no 

 lower-stage form had survived the Oneida Conglomerate. 



In the Leptsenoid type this group is the lowest point at which 

 the Strophodonta depressa, Atrypa affinis, and the remarkable form 

 Chonetes cornuta are seen. The first, with the crenulated hinge- 

 line, reappears in the Coralline limestone of Schoharie. 



Lastly, we have the genus Pentamerus, unknown below, and mark- 

 ing the middle stage. There are six forms, if not eight (Hall), between 

 the Clinton group and the Onondaga Limestone (Devonian) inclu- 

 sive, and not seen higher or lower. In New York, it is usually in 

 casts. Of the Monomyaria and Dimyaria, only five of the former 

 have been met with. Far from conspicuous, even these are rare 



