CANANDAIGUA AND NAPLES QUADRANGLES 27 



Styliola (Styliolina) fissurella and from that fact 

 has taken the name of Styliola limestone, by which it has been 

 generally known. The horizon is well marked and divides the 

 mass of Genesee deposits into nearly equal parts in this section. 

 It is a persistent stratum and has been traced to the east as far 

 as Seneca lake and westward to Lake Erie. The character of this 

 rock is well displayed at the typical outcrop on the shore of the 

 lake at the foot of Bare hill or, as it should be termed, Genundewa. 

 Here it consists of three layers of rather soft and slightly shaly 

 limestone, the rock being impregnated throughout with myriads 

 of the shells of Styliola; is highly bituminous and hence very 

 dark when fresh. The lowest of these layers is 8 inches thick, 

 the second, 7 feet higher, is 6 inches and the third, 6 feet above, 

 10 inches, making the total thickness of the entire band including 

 the intervening shales, 15 feet. These layers increase in thick- 

 ness westward, become less shaly and more nodular, and are event- 

 ually consolidated. On account of the durability of this rock 

 it is a permanent feature in all exposures of this horizon and as 

 its peculiar character makes them easily recognizable the 

 Genundewa limestone is important as a stratigraphic bench 

 mark. The rock is of singular interest from a paleontologic point 

 of view as will be noticed hereafter. Its calcareous nature being 

 largely due to fossil remains it has afforded a fauna of consider- 

 able scope. We find the best exposures of this limestone in the 

 county in the cliffs north of Hicks point and in the Seneca point 

 ravine where it produces the first cascade, also in the Victoria 

 glen and Foster ravine and on the south branch of the Menteth 

 brook where it produced the high cascade f mile south of 

 Cheshire. The point last named is the spot at which the rock 

 was originally located by the writer, though specimens from it 

 had been generally known to students for some time before. It is 

 also displayed admirably at the mouth of the Wilder ravine at 

 Bristol Center and in the ravine on the opposite side of the 

 Bristol valley. In Mill creek or Mill gull in the town of Rich- 

 mond there is an exposure several rods long in the bed of the 

 stream and the limestones are well developed and highly fossili- 

 ferous. 



