258 Dawhins—Rhetic Beds. 
careful examination of these beds in the West of England, I was 
able to trace the downward extension of the formation into the Grey 
Marls, until that time classed with the Keuper. My reason for 
treating, in the pages of this Magazine, of subject-matter that has 
already been embodied in a paper just published in the Quart. Journ. 
Geological Society, vol. xx. p.396, is that new evidence has been 
adduced since the latter was written, inclining me to modify some of 
the views therein expressed. I purpose, therefore, to treat of the 
beds in question in three groups :—first, the White Lias or Upper 
thetic; secondly, the Avicula-contorta-series or Middle Rheetic ; 
and lastly, the Grey and Black Marls and Marlstones up to the pre- 
sent time classed with the Keuper Marls, or the Lower Rheetic. 
Il. The White Lias—Immediately underlying the dark-blue shales 
and thinly bedded limestones of the Ammonites-planorbis-zone, 
which in the Poulden Hills, and near the villages of Butleigh, King- 
weston, Charlton-Adam, Kingsdon, Long-Sutton, and West Hatch 
are characterized by Myacites unionoides, occurs the White Lias, 
composed of a series of earthy limestones, thinly bedded, and sepa- 
rated from each other by loose earthy marl. Sometimes the lime- 
stones are very hard, and of a pinkish tinge, as at West Hatch, where 
also some of the layers are very much water-worn, and bored by 
Pholades. More generally, however, the beds vary from a milk- 
white to a dark grey colour. The following section of the White 
Lias at Long-Sutton is a fair example of the beds and their fossils 
in the West of England, and is important as showing the total thick- 
ness of the White Lias, from the Ammonites-planorbis-shales above, 
to the Avicula-contorta-series below :— 
7 inch. Soft grey Lias, earthy, 
13 ,, White marly earth. 
28 ,, Soft grey earthy Lias: Modiola minima, Lima pectinoides. 
16 ,, Two layers of earthy grey Lias. 
4 ,, Grey shale. 
9 ,, Hard grey Lias. 
24 ,, Six layers of earthy marly Lias. 
12 ,, Hard grey Lias: casts of Corals, Cladyophyllia (?). 
18 ,, Six layers of soft earthy Lias: Modiola minima, Lima punctata. 
4 ,, Hard grey Lias, with worn surface; evidently an old sea-bottom. It 
burns into ‘ White Lime.’ 
5 ,, Earthy grey Marl: Cardiwm Rheticum, Modiola minima, Pleurophorus. 
56 ,, Five layers of earthy grey Lias, without shale. It burns into good lime, 
In thickness the White Lias varies considerably, even over small 
areas, measuring 9 feet at Beer-Crowcombe, and 82 feet at Saltford, 
near Bath. Is average thickness in West and Central Somerset is 
15 feet. 
Paleontologically, it is remarkable for the rarity of specific 
forms; and, so far as I know, it does not possess any one species pe- 
culiar to itself, excepting, perhaps, a small Coral (Cladyophyllia?) 
found at Long-Sutton (see preceding section), and also near Theale. 
In the absence of Ammonites, it contrasts with the beds above ; in 
the absence of Vertebrates, with those above and below. In the 
paper before alluded to, I was inclined to consider it the passage- 
