CONTRIBUTIONS TO PALiEONTOLOGY. 91 



DICTYOPHYTON NODOSUM ( n. s.). 



PLATE III. FIG. 2. 



A FRAGMENT two and a half inches in length, being an impression 

 in shaly sandstone, preserves the marks of two longitudinal ranges 

 of rounded nodes, there being six nodes in each longitudinal row 

 in the length indicated. 



This species differs from the precediDg, in having the longitudinal rows 

 of nodes more nearly parallel, smaller and more clearly arranged in rows, 

 while they are not angular. The surface is finely reticulated by longitudinal 

 and transverse strise. 



Geological formation and locality. In the shaly sandstones of the Che- 

 mung group in Cattaraugus county. 



In the illustrations, I believe I have shown that we have several very 

 distinct species of this group of fossils ; and from the localities cited, it 

 will be observed that they have a comparatively wide geographical range, 

 especially when it is considered that they occur in a sedimentary formation 

 which varies in condition and consistence at moderate intervals. Although, 

 with one exception, the New-York and Ohio forms are all specifically dis- 

 tinct, they are closely allied as a group. Knowing only these nodiferous 

 subangular stems? I cannot insist that they are identical in mode of growth 

 with such forms as Dictyophyton newherryi and D. redfieldi, for we have 

 yet nothing to prove the character of the upper part of the frond in these 

 species. 



The generic term Uphant^nia must for the present be restricted to the 

 original specimen, no other congeneric form having been obtained. 



In all the collections made in the State of New- York from the Hamilton 

 group, no fragment resembling the Dictyophyton has come under my 

 notice. Within New-York, these fossils are restricted to the Chemung 

 group ; and their occurrence in Ohio, in rocks below the Conglomerate, has 

 always been regarded by me as strong evidence of the equivalency of the 

 formations. The paucity of species of fossils in the Ohio rocks identical with 

 those of New-York has lately furnished an argument against the equivalency 

 of age of these formations ; with what force, I leave to geologists to decide. 

 The same doctrines, carried out in their application to other formations, 

 would decide all the sedimentary groups of the Mississippi valley to be 

 distinct from those of New- York. The requirement of specific identity 

 among marine fossils to determine geological equivalency can never be ful- 

 filled when sedimentary formations are studied over wide geographical areas. 



