108 Prosser—Fossils in Millstone-grit. 
characters. Whether the Millstone-grit accompanying the whole 
extent of the Flint Coal-field partakes of the fossiliferous character, 
_the writer is not prepared to state, but he has proved it to be so over 
a considerable extent of country. In one instance, at least, the grit 
is absent from the series, namely, at Selattyn, about five miles from 
Oswestry, where the Coal-shales lie directly and unconformably on 
the Silurian slate-rocks of Selattyn Hill.* 
The Millstone-grit is well developed in several places in the North- 
west of Salop, and the South-east of Denbighshire. It crowns the 
summit of that fine escarpment of Mountain-limestone called the 
Eglwysegle Rocks,’ in the Vale of Llangollen. Continuing thence over 
‘Trevor Rocks,’ it appears as a compact, close-grained sandstone at 
Pont-Cefn ; while in the neighbourhood of Oswestry it is seen at 
Selattyn and Porkington; also on the summits of Cern-y-bweh and 
Mynydd Myfyr; in both of which localities the beds have a consider- 
able inclination. The lowest members, however, of the formation are 
best studied on Sweeney Mountain, where they are much exposed, 
and whence they descend by low smooth undulating eminences to 
the plain below. 
Murchison divides the Millstone-grit of the North-Welsh Coal- 
field into—Ist. ‘Light-coloured siliceous sandstone, forming ‘a 
porous rock, made up of fragments of chert imbedded in a matrix 
of fine white clay.’ 2nd. ‘ Whitish or pinkish sandstone.’ 3rd. ‘Other 
and lower beds, forming the summit of Sweeney Mountain, are 
coarser, containing distinct pebbles of quartz’ (Sil. Syst. p. 144). 
But, inasmuch as the lithological characters of the same bed vary 
considerably in different localities, the above triple division is by no 
means constant over any great extent of country. The following 
section by Sir Roderick, through the Millstone-grit of Mynydd 
Myfyr, indicates the relative position of these strata—namely, be- 
neath the shales of the Coal-measures, and above the Carboniferous 
Limestone (Sil. Syst. pl. 30, fig. 14). 
Mynydd Myfyr, Coal-shafts through 100 feet 
1000 ft. 
W. of Permian sandstone. HE. 
I 
a b ¢c ad e 
Section of the Carboniferous Rocks near Oswestry. (After Murchison.) 
a. Carboniferous b. Red Sandstone. e. Coal-field of Os- 
Limestone. c. Caleareous Grit. : ee westry. Coal-mea- 
d. Red Sandstone, Chert, Millstone-grit. sures, obscured by 
and Grit. gravel, 
Murchison was one of the first to notice the fossiliferous character 
of the Millstone-grit of the North-west of Shropshire ; for, in 1839, in 
his description of these strata, he states that ‘Fragments of Encrinites 
and Corals are also found in these beds’ (Sil. Syst. p. 144). About 
the year 1856 Mr. Meredith, then of Oswestry, now in Australia, 
* Phillips and Conybeare’s Geol. of England and Wales, p. 419. 
