George Barroic — On a Marine Bed in the Yorksliire Oolite. 553 
descending Order, at tliis point, called Walk-mill Force, on tbe 
Six-inck Maps : 
(«) Ten feet of Sandstone, hard and dense at top ; flaggy at base. 
(&) Four feet of shale, ferruginous and sandy in upper part, much resembling 
the shales of the Middle Lias Ironstone. 
(c) Five inches of dense earthy ironstone. 
(d) Five feet of shales, similar to ( b ). 
(e) Fourteen inches of ironstone weathering into blocks, and full of com- 
rainuted fossils. 
(/) Shales of Estuarine series. 
(o) Tkis sandstonekas, I tkink, been noticed by Mr.W. H. Hudleston, 
F.G.S., in a paper on tbe Lower Oolites of Yorkskire, read before 
the Geologists’ Association in November. 1873, and published in 
August, 1874. Tbe bed is remarkable for the density of the upper 
part, wkich causes it to weather out as a small overhanging cliff in 
the steep sides of the gorges of the district, by wkich character 
alone it may be at once identified. The lower part being softer 
weathers away more rapidly. According to Mr. Hudleston the fossils 
found in it are Pholadomya S&manni and a Modiola, the latter of 
wkich I have found myself. The sandstone, however, contains but 
few fossils, and those very much scattered, and badly preserved. 
The thin bed of Ironstone (c) contains a very large number of 
fossils, but in most cases the shell is replaced by a white earthy 
powder, or paste ; and the complete preservation of the shell is 
rare, thus causing some difficulty in the identification of the species. 
The following are the more abundant : — Littorina sp., Astarte 
minima ,° Nucula lachryma ,° Trigonia striata ,° Cardium ° sp., Ceri- 
thium quadrivittatum (?), Pinna caneata (?), Gervillia acuta, Cucullcea. 
There are several other species, but undeterminable from their 
occurring only as casts. In the middle of the shale below is a thin 
aluminous band, very soft, and tasting strongly of alum. 
( e ) This bed of ironstone, first mentioned by Bewick, is a nearly 
white, hard stone, full of comminuted skells, and much resembling 
the lower part of the Pecten-band (Middle Lias) at Grosmont. Its 
characteristic, however, is the extraordinary abundance of a Pliola- 
domya, wkich occurs ckiefly in the weathered joints of the ironstone, 
and in such numbers that a hundred full-sized specimens may be 
collected in a few hours. It also contains a Myacites, vertically 
imbedded, in considerable numbers ; the other fossils being much 
the same as those in the bed above, only not occurring in such good 
preservation. 
This bed of ironstone is about 120 feet above the top of the Upper 
Lias in this district ; the whole Estuarine series being much tkinner 
than at Peak. 
It is in Winter Gill, however, a small tributary of Glaisdale Beck, 
about five miles west of the Eller Beck section, that this marine 
bed attains its greatest known thickness, as well as its most interest- 
ing development. Unfortunately a clirnb of nearly 800 feet, over a 
rather rough road, will probably deter all but the more ardent spirits 
from studying the section that is here so well shown. 
* Abundant. 
