Vol. 57.] UPPER COAL-MEASURES OF THE MIDLANDS. 255 



A description of these subdivisions has a^^peared elsewhere,^ and 

 need not be repeated. The main characters are given in the table, 

 while the position of the various bands of limestone and Black- 

 Band ironstones are shown in vertical sections Nos. 1-4, fig. 1, p. 252. 

 I will confine mj^self, therefore, to such evidence as the district 

 affords, in settling the question of the relation of the subdivisions one 

 to the other and to the productive series. 



Let us first consider the relation of the subdivisions one to the 

 other. 



Relation of the Etruria Marl Series to the 

 Black- Band Series. 



The base of the Etruria Marls is generally, but not invariably, a 

 greenish-yellow grit. When this is absent, red marls rest directly 

 on the top of the Black-Band Series. Grits of a kindred character 

 are of frequent occurrence throughout the subdivision, and are 

 persistently and strongly developed near the summit, where they are 

 much coarser than those at the base. Their presence, therefore, 

 does not mark any particular line of erosion. That the basal grits 

 do not indicate a discordance is shown by the fact that they always 

 occur a few feet above a Black-Band ironstone known as the Top lied 

 Mine or Half- Yards, that is, subjected to the law of thickening and 

 thinning of the strata to be mentioned later on (p. 258) ; they are 

 developed at the same vertical distance above the Bassey Mine Coal 

 or base of the Upper Measures. At one locality, Chesterton, about 

 150 feet up in red marls, a thin band of Black-Band ironstone, over- 

 lain by grey grit, is dcc^bloped. The ironstone contains Anihracomya 

 Phillijosii in abundance, a fossil very common in the Black-Baud 

 Series. The Etruria Marls also contain thin limestones, with ento- 

 mostraca similar to those found in the Black-Band Series. It is, 

 moreover, noticeable that bands of red marl are present in the middle 

 and towards the summit of the I31ack-Band Series (Hampton's Marl- 

 Pit, Shelton, Cannon Street, Ladyswell, Longton Hall), thus showing 

 the oncoming of the conditions under which the Etruria Marls were 

 deposited. The Etruria Marls are, therefore, stratigraphically and 

 palaiontologically allied to the Black-Band Series. 



Relation of the Newcastle-under-Lyme Series 

 to the Etruria Marls. 



The Newcastle-under-Lyme Series can be clearly demonstrated to 

 be conformable to the Etruria Marls by the limestone at its base 

 int^ariably occupying a position 30 to 50 feet above a band of lime- 

 stone that occurs near the summit of the Etruria Marls. Instances 

 of the gradual passage of the red Etruria Marls into the grey shales 



^ ' Summa 

 Njrth Staffs 



ry of Progress of the Geological Survey for 1898-1899 ' Proc. 

 Field Chib, vol. xxxiv (1900) pp. 9:)-97. 



