NIAGARA GROUP. 



175. 



It is not probable, therefore, that these fossils could have lost all indication of their original 

 structure, had they been Gorgoniae. 



Fig. 1 a. A large nearly circular frond of this species. 

 Fig. 1 b. An enlargement from a similar frond. 



Position and locality. In the shale at Lockport, Rochester, Marshall's mill, Wolcott, and 

 at nearly all the exposures of the shale along the range from Rochester westward to the 



Niagara river. {State Collection.) 



570. 2. DICTYONEMA GRACILIS (n..9/j.). 



Pl. XL G. Fig. \ a-d. 

 Gorgonial Rep. 4th Geol. District, p. 115, fig. 2, 1843. 



Frond circular or flabelliform (probably cyathiform in its growing state), composed of slen- 

 der bifurcating and slightly diverging branches, which are united laterally, and at long intervals, 

 by very slender filaments ; branches irregularly striated or indented, sometimes having uneven 

 or subserrate margins ; texture like the preceding, with an outer black film and interior sub- 

 calcareous stipe. 



This species is readily distinguished from the preceding, by its more slender and neatly 

 defined branches, with more distant connecting dissepiments, which are likewise extremely 

 slender. It bears a close resemblance in structure and mode of growth to Fenestella, with 

 the difference in texture and absence of cells on one side. 



This species has not been observed in circular fronds like the preceding, but, judging from 

 some crushed specimens, of which one side and a portion near the base is visible, it grew in 

 expanded funnel-shaped or cyathiform fronds. There is no apparent difference in the texture of 

 the branches on the inner or outer side, though the lateral margins may have been celluliferous 

 as in the Graptolites. 



Fragments of this species have been observed, of a size which show that had the frond been 

 circular, it would have had a diameter of ten inches or more. 



Fig. 1 a. A portion of a frond, showing the branches neatly defined, and spreading only in a 



moderate degree. 

 Fig. 1 b. A part of another frond, where the branches appear to spread more rapidly, but have 



otherwise the essential characters of the preceding. 

 Fig. 1 c. An enlargement, showing the indented or corrugated surface of the branches. 

 Fig. 1 d. An enlargement of several branches, where the margins appear indented or subserrate. 



Position and locality. This species has been observed only in the shale at Lockport. 



( State Collection ) 



