4 BONNE Y : ON THE ORIGIN OF THE BRITISH TRIAS. 
Humber." It varies in colour from red to yellow, exhibits 
current-bedding, contains " millet seed " beds, and much 
resembles the Lower Sandstone, but is rather finer grained. 
Thus the Bunter as a whole disappears south of a line running 
through the southern parts of Leicestershire, Staffordshire, and 
Warwickshire, and is not again found north of the Bristol 
Channel.* In the southern area its chief development is between 
the mouths of the Exe and the Axe, where the Pebble Bed 
reaches a thickness of about 100 feet, the Lower Sandstone 
is apparently wanting, and the Upper is represented by a soft 
sandstone measuring about 450 feet. Some differences of 
opinion exist about its exact limits, but into these we need not 
enter. Suffice it to say that the dimensions of the southern 
Bunter are much inferior to those of the northern, for it 
thins rather rapidly towards the north and the east, dying out 
in the course of some 30 miles from the coast. 
The Keuper, as a whole, exhibits no such interruption, and 
its deposits differ considerably in their mineral character. It 
also (I exclude the Rhaetic) often admits of a triple sub-division — 
the Lower Sandstone, the Waters tones, and the Red Marl. 
The first, more often grey than red in colour, is occasionally 
pebbly and has a breccia at its base, the third is a red clay, 
banded with pale greyish-green, sometimes containing masses of 
rock salt and of gypsum, and with occasional lenticular inter- 
calations of sand or breccia, the latter having been formed 
near shore lines, while the second deposit, the Waterstones, is 
obviously a transitional one, rather thin beds of sandstone, 
commonly grey in colour, alternating with layers of Red Marl. 
East of the Pennines the Keuper sandstone is sometimes wanting, 
but it is about 120 feet thick near Nottingham, and is well 
developed around Derby. In South Lancashire, Cheshire, Staf- 
fordshire, and Shropshire it is often some 200 feet thick, probably 
attaining, according to Professor Hull, its maximum thickness, 
from 400 to 450 feet, in the neighbourhood of Stourbridge. 
Its basement often consists of breccia, like that of the Bunter, 
* I have not taken account of the St. Bees sandstone, now generally 
regarded as Bvrnter, because so far as I am aware we have no means of 
determining its exact position in that group. ]Mr. H. B. Woodward 
says it varies in thickness from 500 to 2,000 feet. 
