STUDY OF THE GRAPTOLITES. 21 



Hudson-river formation may be in the Utica slate, which, owing^ to the 

 disturbed condition of the strata, is not separable from the succeeding 

 slates. 



In the Hudson-river formation the characteristic graptolites, of nume- 

 rous species, have been found, in greater numbers than elsewhere, at 

 Norman's Kill, near Albany ; but they occur at Stuyvesant's Landing, and 

 at the city of Hudson ; while some species have been found near Baker's 

 Falls on the Hudson-river, and at Ballston^ and Saratoga, New-York. 

 Graptolites of species identical with and similar to those of the Hudson-river 

 formation have been found by Dr. Emmons in the shales of Augusta 

 County, Virginia, and also in Tennessee. 



The more characteristic species of the formation, G. pristis, G. bicornis, 

 G. ramosus, G. sextans^ G. divaricatus, and G. gracilis, have been recog- 

 nized among the collections of the Canada Geological Survey, from the 

 Hudson-river formation in the valley of the St. Lawrence-, and a species of 

 Diplograptus occurs in the Utica slate at Lake St. John. In the exten- 

 sion of this formation westward, a few species only have been found iu 

 Central and Western New- York ; among these, G. pristis is the most com- 

 mon, while G. bicornis is more rarely seen. In Ohio, we have no more 

 than two species from rocks of this formation; while extensive collections 

 from the same formation in Wisconsin and Iowa have afforded only three 

 species (all unlike those from Cincinnati), and one of these has been found 

 in beds of the same age in Illinois. In the catalogue of fossils appended 

 to the Geological lieport of Missouri, no mention is made of the occur- 

 rence of Graptolitidae in any of the formations. 



The great accumulation of materials at the epoch of the Hudson-river 

 formation has been in the direction from northeast to southwest ; and along 

 this line the black and dark colored graptolite schists, alternating with 

 coarser beds, have collected in much greater mass than in any other part 

 of its extent. In the northwestern counties of New-York, Jeffeison and 

 Oswego, where the formition has a thickness of more than a thousand 

 feet, the graptolites are comparatively few in species, and not of common 

 occurrence. The gradual attenuation of the rocks of this formation 

 towards the west is marked by the extreme paucity of graptolitic forms. 



The graptolites of the Clinton strata have not, to my knowledge, been 

 found beyond the limits of Western New-York ; and both their horizontal 

 and vertical range is very restricted. The graptolitic forms of the Niagara 

 formation {Dictyonema and Inocaulis) are very limited in their geographi- 

 cal extent. 



The Dictyonema of the Upper Helderberg and Hamilton formations are 

 known to occur in New- York and in Ohio; and in the northwest, a species 

 has been found in the Upper Helderberg limestone on Mackinac Island. 



This distribution of the Graptolitidae, as well as their general association 

 with other fossils, together with the nature of the sediments, would indi- 

 cate the existence of quiet water and proximity of the coast-line as their 

 habitat, and as the zone of their greatest d«velopment. 



