52 NEW YORK STATE MUSEUM 



sented is but slightly increased by the addition of a few of the 

 forms that first appear in the Genundewa limestone. 

 The following are the more common fossils : 



Bactrites aciculum (Hall) Buchiola retrostriata (v. Buck) 



Pleurotomaria rugulata Hall Lingula spatulata Vanuxem 



Pterochaenia fragilis (Hall) Orbiculoidea lodensis (Vanuxem) 



Spheric and oblong concretions occurring singly or in rows are 

 common and have been collected in many places on account of their 

 symmetry or their sometimes curious forms suggestive of " petri- 

 fied turtles/' " Indian skulls," " stone hats," " stone ducks " etc. 



No exposure of these beds but the one at the mouth of the 

 gorge, which is continuous up the river for about a mile, is found 

 on these quadrangles, but they may be seen to good advantage 

 above the falls in the Moscow ravine, 3 miles farther north and 

 in the upper part of the Fall brook gully. 



The name "West River shales" was first applied to these be -Is 

 above the Genundewa limestone by Clarke and Luther in Bulletin 

 63, 1904, on account of their abundant exposure in the ravines of 

 the West river valley in Yates county and to meet the require- 

 ments of a stratigraphic term for the residuary member of the old 

 Genesee division. 



Standish shale 



At the top of the West River beds there are in this section a 

 few lighter colored layers, some clayey, others slightly arenaceous, 

 altogether about 3 feet in thickness. 



This lighter band which has the lithic characters of the shales 

 and flags of the Portage group and contains a few fossils from 

 both the Genesee and Portage faunas, is hardly noticeable here, is 

 more fully developed in the Canandaigua lake valley and is known 

 as the Standish shales and flags. It is not represented in the 

 coloring on this map. 



Middlesex shale 



This passage bed is succeeded by 32 feet of densely black 

 bituminous slaty shales that show a marked contrast to the 

 West River shales lithologically and in being almost entirely 

 barren of fossils except lignites, which are common, and a few 

 fish plates and scales, which are very rare. A few small lingulas 

 found in this horizon at the mouth of Pike creek on Lake Erie 

 are the only other fossils collected from these beds in the western 

 part of the State and they belong to the species found in similar 

 black shales higher in the Portage group, L. ligea Hall and 

 L. spatulata Vanuxem. 



