O NEW YORK STATE MUSEUM 



the Genesee river, for the lower beds are hig-hly bituminous and 

 regularly slaty and it was to indicate this bituminous character that 

 the rock series was specially and separately designated. Regarding 

 the Genundewa limestone as the boundary between the lower and 

 upper divisions we have heretofore introduced as the designation 

 for the latter the term West River shale. Here these shales are dark 

 blue gray, medium hard, slightly calcareous with frequent thin layers 

 of black shale. In weathered cliffs the mass has a dull black appear- 

 ance. In the exposures on this quadrangle the formation attains a 

 thickness of 35 feet. In it, 15 feet above the Genundewa limestone, 

 is a concretionary calcareous layer 10 to 12 inches thick, sufficiently 

 compact to appear as a layer of soft gray impure limestone; sym- 

 metrical concretions usually small are common in the upper beds. 

 This upper calcareous la3'er was noted by D. F. Lincoln in his survey 

 of Seneca county as occurring in Lodi glen. 



Exposures of this West River shale are found only in the cliffs 

 along the lake shore on the west side from Rock Stream point south- 

 ward for about 3 miles when it dips under the lake. It comes up 

 again at the head of the lake arid the top is slightly exposed at a 

 small culvert on the Northern Central Railroad H mile north of the 

 Watkins railroad station and 6 feet above the lake. Except for a 

 few insignificant outcrops it is mantled with drift and talus on the 

 east side of the lake within this quadrangle but farther north the 

 series is shown in the glen at Lodi and at Highland landing. On 

 Canandaigua lake it is seen at Woodville and in the ravines at the 

 north; also in the bluff at the mouth of the Genesee gorge at Mt 

 Morris and at many places westward to Lake Erie. This division, 

 like those previously mentioned, is thicker and its characteristic 

 structure more highly developed in Ontario and Livingston counties ; 

 thence westward it grows thinner but without appreciable change in 

 the character of the sediment. 



Fossils are rare in the shales ; L i o r h y n c h u s m u 1 1 i - 

 c o s t a , C h o n e t e s 1 e p i d u s , A m b o c o e 1 i a u m - 

 b o n a t a , P t e r o c h a e n i a f r a g i 1 i s and B u c h i o 1 a 

 speciosa occasionally appearing. The concretionary limestone 

 at the top carries other fossils : N u c u 1 i t e s o b 1 o n g a t u s , 



