MARCELLUS LIMESTONES AND THEIR FAUNAS 129 



portion of tlie section however simply serves to emphasize the 

 gradual passage of the bituminous shale fauna into that of the 

 calcareous shales and to establish the proper conception of the 

 typical Marcellus fauna as that of these black shale beds and 

 bands. 



The Stafford limestone in this section lies at 828 feet, or 173 

 feet below the assumed top of the formation, the overlying strata 

 being shales. It is here 2 feet thick, and is immediately underlain 

 by 4 feet of black and bituminous shales with Liorhynchus, 

 Panenka, Chonetes mucronatus, etc. the usual species 

 of the typical shale beds. Thereunder follow 22 feet of black 

 shales without fossils, this mass underlain by a thin shale bed 

 with the usual species. From here are 13 feet to the top of the 

 Onondaga limestone. Its position is thus about 50 feet above 

 the Onondaga. The section is complete and brings out lucidly 

 the thickening of the lower beds by calcification in their west- 

 ward extent. 



The Stafford limestone appears at various spots across the 

 western district in the depression lying back and south of the 

 Onondaga limestone escarpment. It is to be seen near Baggerly 

 Corners, Ontario co. on the Phelps-Hopewell line road. At Little- 

 ville, 2 miles south of Avon, Genesee c6. it appears in a gorge 

 behind the mill with dark shales above and below. About a 

 mile south of the station in Avon, in a brook east of the Erie 

 railroad tracks, is another exposure, and the rock is again seen 

 a short distance down the stream and beneath a mass of dark 

 shale, another limestone outcrops, which appears to be the 

 equivalent of the lower bed lying at 854 feet in the Livonia shaft, 

 which we have suggested as marking the probable horizon of the 

 Agoniatite limestone in this western region. Here it rests 

 directly on the Onondaga limestone and stratigraphically is 

 inseparable therefrom. The exposure of Stafford limestone at 

 Stafford, Genesee co. lies about J mile southeast of the station, 

 where it has been quarried at various times. Such a large 

 amount of the material lies exposed here that it makes an admir- 

 able spot for the collection of its fossils. At Leroy there is an 



