LOWER SILURIC SHALES OF THE MOHAWK VALLEY 25 



were found near the top of this last cliff with which end the out- 

 crops in the Canajoharie gulf. 



A series of exposures which to a large degree is complementary 

 to the one just described is afforded by the Flat creek ravine at 

 Sprakers, two and one-half miles east of the Canajoharie ravine. 



The Glens Falls limestone is finely exposed in this section. It is 

 17 feet thick and consists of thin layers of very fossiliferous lime- 

 stone with shale intercalations near the top and a two-inch con- 

 glomeritic layer at the base, separating it from the Tribes Hill 

 (Fucoidal) limestone. The limestone beds exhibit large ripple 

 marks, small piles of current-swept pebbles and other signs of 

 shallow water conditions. Besides .the fossils noted from the Cana- 

 joharie beds, Eurychilina subradiata was also 

 collected. 



The " Utica " shale comes in, notwithstanding the shaly inter- 

 calations of the upper Glens Falls beds abruptly as a black shale 

 formation. It contains directly at the base : 



Diplograptus amplexicaulis {Hall) (cc) 



Ctenodonta cf. nuculiformis (Hall) (c) 



1 Ten feet above the base abundant Diplograptus 

 (Mesogr. ) putillus and ostracods ( U 1 r i c h i a ? 

 bivertex, Primitiella unicornis, Primitia) 

 were observed, which continued through 20 feet, where also layers 

 with great numbers of Leptobolus insignis and 

 limestone bands filled with Dalmanella testudinaria 

 were observed. 



2 The beds from 30-60 feet above the base furnished : 



Diplograptus amplexicaulis (cc) 



Cyathodictya ? tubularis (cc) 



Leptobolus insignis (cc) 



Ctenodonta cf. nuculiformis (c) 



3 From 60 feet above base upward there were observed besides : 



Diplograptus amplexicaulis (cc) 



Orthoceras sp. 



Lingula curta . (c) 



4 75 feet above base besides Diplograptus amplexi- 

 caulis and the ostracods, specimens of Clathrospira 

 subconica (Hall) were found. 



5 From 1 10-20 feet C a 1 y m m e n e s e n a r i a occurs 

 in great abundance and from 125-30 feet fragments of Isotelus 

 and Prasoporas fill the beds. Also at about 135 feet above the 



