34 NOTES ON THE CANNOOK CHASE COALFIELD 
indebted for what we know to those untiring workers in North 
Staffordshire, John Ward, J. T. Stobbs, and Dr. Wheelton Hind. 
Tn the Upper Coal Measures the best known zonal forms are— 
Anthrocomya Phillipsi 
Carbonicula Vinti 
Spirorbis carbonarius 
The last-named occurs in limestone bands; one well defined 
band, 18in. thick, has been traced over a very large area in North 
Staffordshire, and seems to occupy the position of a persistent line 
of sep:ration between the Upper and the True Coal Measures. 
Similar bands have been traced in Warwickshire, Shropshire, and 
Lancashire, and quite recently one was found in a borehole at 
Claveley, in Shropshire, where, at a depth of 420 yards, the Spirorbis 
Limestone was passed through. 
Thinner bands of Spirorbis Limestone exist lower down in the 
formation, and I have found one band 5in. thick in the True Coal 
Measures on Cannock Chase. 
Unfortunately the Cannock Chase Coal Measures are not very 
fossiliferous ; the most abundant form is Carbonicula acuta, which is 
extraordinarily abundant throughout the series, and is too common 
to be of any use for zonal purposes. Another species —Carbonicula 
robusta —is found towards the bottom of the Measures, and is 
a useful indicator of horizon. 
Marine bands are thin beds, containing either in the shale or in 
bullions very characteristic fossils easy to distinguish, such as 
Pecten papyraceous 
Chonetes laguessiana 
Lingula mytiloides 
Nucula gibbosa, &c. 
One such marine band is known to exist in the Cannock Chase 
Coalfield, but its exact horizon has not yet been ascertained. 
