288 New York State Museum 



they were included in the "Hudson River" group and 

 considered of Lorraine or Frankfort age. This forma- 

 tion has a thickness of at least 2000 feet, and consists of 

 grits and sandstones with interbedded black and gray ar- 

 gillaceous shales which form a uniformly alternating 

 series throughout the whole formation. It occurs in the 

 southwest corner of the Saratoga quadrangle and from 

 there extends in a broad belt (six to eight miles wide in 

 the capital district) between Schenectady and the Helder- 

 berg escarpment reaching into the Schoharie valley (at 

 Schoharie village). It is believed to owe its thickness 

 to deposition in a sinking basin in front of the rising 

 Green mountains in the east (Ruedemann). In Albany 

 county the Schenectady beds are overlain by the Indian 

 Ladder beds; farther to the southwest in Schoharie 

 county they are overlain by the Silurian (Brayman 

 shales). The most characteristic fossil of the Schenec- 

 tady beds is the seaweed Sphenophycus latifoliiis. In- 

 cluded in its fauna are the graptolites Dictyonema multi- 

 ramosum, Diplograptus vespertinus, Climacograptus spi- 

 nifer, C. typicalis, and Lasiograptus (Thysanograptus) 

 eucharis; the brittle star Taeniaster schohariae ; brachio- 

 pods as Leptobolus insignis, Dalmanella rogata, Plector- 

 ihis plicatula; the pelecypod Saffordia ulrichi; gastropods 

 as Cyrtolites cf ornatus; the conularid Conularia tren- 

 tonensis var. multicosta; the cephalopods Spyroceras bi- 

 lineatum and Trocholites ammonius ; the trilobites Triar- 

 thrus becki } Isotelus gigas and Cryptolithus tessellatus 

 Eurypterids deserve special mention and include the 

 genera Eurypterus (E. pristinus), Eusarcus (E. triangu- 

 latus), Dolichopterus (D. frankfortensis), Hiighmilleria 

 (H. magna), Pterygotus (P. nasutus) and Stylonurus? 

 (S. limbatus). This fauna contains elements of both the 

 Utica and Trenton faunas and a fauna of its own 



