COMPARISON OF WESTERN SECTIONS 331 



miles east, where it is 8 feet above their main ore bed (9 : 57). In the 

 well at South Granby a fourth thin ore and limestone are inserted be- 

 tween the graptolitic shale and those slialy members above which seem 

 to represent shale replacements of much of the upper limestone of the 

 Rochester section. Meantime the lowest ore bed, so persistent from the 

 Rochester meridian, has abruptly disappeared (9 : 35) between Red Creek 

 and Martville (compare text-figure 4). 



NoAV the exceedingly interesting ])oint brought out by Hartnagel (9: 

 21, 22) is that in the absence of good continuous exposures the middle 

 limestone of the Wolcott region was confused with the lower limestone at 

 Rochester^ both of them carrying Pentamerus ohlongus abundantly at 

 their respective localities; and in consequence the middle shale at Sodus, 

 with its pearly layers and purple color, was forcibly connected with the 

 bright green barren basal shale of Rochester. It will be seen that the 

 latter is nearly or quite missing on the meridians of Sodus and Wolcott, 

 while its overlying limestone has become so shaly as to seldom outcrop. 

 In the typical Sodus section, that of the old Shaker settlement on Second 

 Creek, this lower limestone with its ore bed is beneath the waters of Sodus 

 Bay. The long list of fossils described by Hall from the "lower shale at 

 Sodus" are all forms of the middle or purple shale, which must accord- 

 ingly take the name of Sodus shale, and whose place is in the lower part 

 of the "upper shale'^ at Rochester. Similarly the only limestone with 

 Pentamerus at or near Wolcott is the middle limestone, which is absent 

 from the Rochester section, and this must retain the name Wolcott lime- 

 stone, while both the lower limestone and the basal shale at Rochester 

 remain yet to be named. The necessity for these changes is discussed 

 again beyond. 



A glance at the chart shows how easy it was for this confusion to arise. 

 Had w^e not the intervening section at Ontario, with its thinned basal 

 shale and absence of the Thorold, we might readily ignore the incisive 

 evidence of the fossils and repeat Hall's error, which was the more ex- 

 cusable since a shale seeming to occupy the position of our basal green 

 shale carries the Sodus Coelospiras at Niagara. This Niagara section is 

 accordingly also given on the chart, together with two others to the west 

 as reported by Schuchert (12 : 308-311), in order to show that the "Clhi- 

 ton basal shale" at Niagara is not the barren green basal shale of Roches- 

 ter; for, according to Logan (Geology of Canada, 313)", the latter re- 

 appears in the next section west of Niagara and there carries the IMcdina 

 worm burrow, Arthrophycus. These relations, as understood by Schu- 

 chert, are shown in the diagram, wJiich tlius clearly brings out a discon- 



Footnote o is on page .'534. 



