LOWER SILURIC SHALES OF THE MOHAWK VALLEY 33 



rendered inaccessible the contact exposed in the river bed. This 

 contact was recorded by Mather (title 2, p. 394) as follows: 



At a little distance below the ferry on the Saratoga shore, at and 

 near the sawmill, the junction of the slate and Trenton limestone, 

 and the gradation of one into the other by interstratification, with 

 the numerous and beautiful fossils, which are intermingled near 

 their junction, can easily be examined when the river is low. The 

 trilobite, the Nuttainia concentrica of Eaton [ T r i - 

 nucleus concentricus (Eaton) ] , is extremely abundant, 

 and on one specimen of a thin band of limestone six inches square, 

 from the slate, were no less than ten of these trilobites, some of 

 which were entire, and one of the Triarthrus becki. 



While these transition beds can not be seen any more in place, 

 the construction of the mill race for the Fenimore Paper Mill 

 opposite Hudson Falls has brought to light a great quantity of the 

 transitional rock which has been dumped along the river bank just 

 above the mill. It consists of dirty grayish-brown limestone with 

 black shale seams. The limestone is very f ossilif erous ; the follow- 

 ing fossils have been noted: 



Mesotrypa quebecensis (Ami) 

 Schizocrania filosa Hall 

 Dalmanella testudinaria (Dalman) 

 Plectambonites sericeus (Sow.) 

 Triarthrus becki Green 

 Trinucleus concentricus {Eaton) 

 Isotelus fragments 



The shales at the falls contain : 



Corynoides gracilis Hopkinson 

 Diplograptus amplexicaulis Hall 

 Climacograptus spiniferus Ruedemann 

 Lasiograptus eucharis (Hall) 

 Trocholites ammonius Conrad 



These shales can thence be followed about two miles through a 

 fine gorge to the falls at Fort Edward, where there are found : 



Corynoides calicularis Nicholson 

 Diplograptus cf. euglyphus Lapworth 

 Trematis terminalis (Conrad) ? 

 Orthoceras arcuolineatum nov. 



From Fort Edward this belt of shale can be followed down the 

 Hudson river for several miles. Occasionally, as in an outcrop two 



