30 NEW YORK STATE MUSEUM 



Burls in the higher sandstones contain: 



Manticoceras patter soni (Hall) . Orbiculoidea sp. 



Orthoceras bebryx Hall Leptostrophia mucronata {Conrad) 



Liorhynchus inesacostale Hall Grammysia siibarcuata Hall 



Cyrtina hamiltonensis Hall Cladochonns sp. 



and masses of plant remains in which fragments of Lepidodendron 

 are frequent. A considerable number of additional species have 

 been collected from this formation on the Ithaca c[uadrangle where 

 it is favorably exposed about the head of Cayuga lake. 



From Lake Erie eastward as far as Seneca lake the Cashaqua 

 shale succeeds the black Middlesex shale and is overlaid by another 

 band of black shale known as the Rhinestreet black shale, a forma- 

 tion that reverses the usual order and decreases in thickness toward 

 the east and is not recognized with certainty in the Cayuga lake 

 valley. Both these formations are absent in the Genoa district. 

 Near the south line of the Genoa quadrangle the basal layer of the 

 Cashaqua is a compact sandstone nearly 3 feet thick that thins out 

 toward the north and disappears in a few miles but the contact is 

 still plainly marked by the abrupt change in the color of the rocks. 



Hatch shales and flags 



This formation as exposed on the slopes of Hatch hill in the Canan- 

 daigua lake section is clearly defined by the Rhinestreet black shale 

 upon which it rests and the Grimes sandstones by which it is over- 

 lain. It there, as here, consists of shales and thin sandstones in 

 frequent alternations, but is thinner and less arenaceous, and though 

 it contains a few fossils, they all belong to the Naples fauna from 

 which brachiopods are^ with the exception of a small Lingula, en- 

 tirely absent. 



In the Seneca lake section these beds are found to contain a few 

 brachiopods and the lamellibranchs and cephalopods of the Naples 

 fauna are less common. In the Cayuga lake valley, and specially in 

 the southern part, the number of species of brachiopods and lamelli- 

 branchs that are not known in the horizon of these beds in the Naples 

 or Genesee river section is greatly increased, while the representa- 

 tives of the Naples fauna have almost, though not quite, disappeared. 



The thickness of this formation on the Genoa quadrangle is 350 to 

 375 feet, lack of favorable exposures making precise measurement 

 impracticable. The numerous exposures of this formation about 

 Ithaca 6 to 10 miles south of the Genoa quadrangle have afforded 

 about 50 species of fossils constituting the well known Ithaca fauna. 



