622 NEW YORK STATE MUSEUM 



A.T. Though the individual members of the series frequently 

 change in character and sometimes pinch out entirely within 

 short distances the formation as a whole is continuous for many 

 miles toward the east and west. As the subjacent and the 

 overlying beds are composed almost entirely of soft shale the 

 sandstones usually produce falls where a hillside stream crosses 

 this horizon and make more or less well denned escarpments on 

 the sides of the valleys. 



The proportion of sandy sediment in the Grimes sandstones 

 as in the flag and shale beds below, is much less in the river sec- 

 tion, but the formation maintains its character sufficiently to be 

 noticeable as a distinct band of flags and thin sandstones in the 

 cliffs on the east side of the river at St Helena, and also 1 mile 

 southwest, where it comes down to the river level near the mouth 

 of Wolf creek, almost exactly west of the exposure at the reser- 

 voir in Naples, at the elevation of 675' to 700' A. T. 



Up to the base of the Grimes sandstones the similarity in both 

 lithologic and paleontologic aspects of the two sections makes 

 correlation simple but at this horizon, in the Naples section, the 

 Portage fauna suddenly and finally disappears, while in the 

 Genesee section it holds its place to the exclusion of all brachio- 

 pods to a horizon that, .stratigraphically, is 700' to 800' higher. 



The last appearance of the normal Portage fauna in the Naples 

 section is in some thin layers of soft shale between flags, in the 

 face of the precipice at the third falls in Grimes gully, and this 

 fauna is found also in similar shales at the same horizon in Tan- 

 nery gully at the High falls. 



24 feet higher and 9 feet below the crest of the falls a 4 inch 

 layer of soft sandstone contains Liorhynchus quadri- 

 cpstatus, Atrypa reticularis, Pro duct e 11a 

 spec! os a, Ambocoelia umbonata var. gre- 

 garia, Leptostrophia mucronata and Orbicu- 

 1 o i d e a sp., an assemblage regarded by Clarke as altogether 

 foreign to the Portage or Naples fauna. These foissils are found 

 along the line of outcrop of this layer for four or five rods on both 



