REPORT OF THE STATE PALEONTOLOGIST 1902 979 



below, the Oswayo contains in many places a fairly good repre- 

 sentation of marine invertebrates, prominent among which is 

 Camarotoechia a 1 1 e g a n i a , which serves as an excel- 

 lent horizon-marker. 



Limestone layer. A few feet above the base of the Oswayo 

 shale, is found in a number of places in New York what seems 

 to be a persistent layer of very impure limestone. It is only 

 one or two feet thick and in places is separated into two layers 

 with several feet of shale between. This limestone is com- 

 posed of innumerable fragments of badly broken brachiopod 

 and other marine shells. It might almost be termed a shell 

 conglomerate. In places it also includes bryozoan remains. 

 One of the best exposures is seen in an abandoned railway cut 

 at the burned power-house on the electric road about a mile 

 north of Olean rock city. It is again found just off the Sala- 

 manca quadrangle on both the present and the abandoned line 

 of the electric road southwest of Knapp's creek in several 

 places. Near the head of Nichols run on the hill southeast of 

 Limestone and at the head of the western branch of Red House 

 brook along an abandoned railway grade just beyond the edge 

 of the Salamanca quadrangle it is again found. It is probably 

 the same as a very similar limestone which the writer has 

 examined at a number of places in McKean county, Pa. and 

 which is called by Ashburner 1 the Marvin creek limestone with 

 the suggestion that it is probably the same as the Lower Mead- 

 ville limestone of Crawford county. 



On the Olean quadrangle a few small areas of Oswayo shales 

 are found on the highest crests north and east of Portville, but 

 they are mainly found on the highest ridges south of the Alle- 

 gheny river and in this region extend up to the base of the Olean 

 conglomerate. Near their top they become sandier and the 

 number of thin limonitic sandstone plates increases. 



On the Salamanca quadrangle the largest areas of Oswayo 

 shales are found south of the Allegheny river. They occur on 

 almost every prominent ridge. North of the river the only 

 areas of any size are those on the ridge crests on either side of 

 Tenmile creek. 



'Ashburner, C. A. Sec. Geol. Sur. Pa. Rep't R. p. 68-69. 



