﻿George Barroic — On a Marine Bed in the Yorkshire Oolite. 553 



descending order, at this point, called Walk-mill Force, on the 

 Six-inch Maps : 



(«) Ten feet of Sandstone, hard and dense at top ; flaggy at base. 



{b) 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 ii-onstone. 



{d) Five feet of shales, similar to [b). 



{e) Fourteen inches of ironstone weathering into blocks, and full of com- 

 minuted fossils. 



(/) Shales of Estuarine series. 



(a) This sandstone has, T think, been noticed by Mr. W. H. Hudleston, 

 F.Gr.S., in a paper on the Lower Oolites of Yorkshire, read before 

 the Geologists' Association in November, 1873, and published ia 

 August, 1874. The bed is remarkable for the density of the upper 

 part, which causes it to weather out as a small overhanging ciiif in 

 the steep sides of the gorges of the district, by which 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 Scemanni and a Modiola, the latter of 

 which 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., Astai'te 

 minima/'' Nucula lachryma/' Trigonia striata/-' Cardium^-' sp., Ceri- 

 thiiim quadrivittatiim (?), Pinna cuneata (?), GervilUa acuta, Cucidlcea. 



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 shells, and much resembling 

 the lower part of the Pecten-band (Middle Lias) at Grosmont. Its 

 characteristic, however, is the extraordinary abundance of a Phola- 

 domya, which occurs chiefly 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 thinner 

 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 climb 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. 



