256 J. H. Cooke — Section in Middle Lias, Lincoln. 



In Handley's Pit four phases of shale deposits are exposed within 

 a vertical range of 15 feet ; and each is separated from the other by 

 a line of ferruginous septaria. When freshly cut, the shales are of 

 a dark-blue colour, but on exposure they weather to a light-grey. 

 In composition they are decidedly argillaceous, with an admixture 

 of carbonate of lime, of mica, and of considerable quantities of iron 

 and silica. The carbonate of lime consists for the most part of the 

 tests of foraminifera, the most predominant of which are Cristellaria, 

 Nodosaria, Cytheridea, and CytliereUa} As a rule the shales are not 

 rich in fossils, although pyritized wood and lignite are very common. 

 In these latter the ligneous structure is always very marked, and 

 when fractured they readily split in the direction of the fibre. 



It is not possible in a general statement to give the thickness of 

 these shale beds, as they vary so much at different points ; the 

 thickness in the section given on p. 254 represents the beds in the 

 centre of the pit, and is on the whole a fair average. 



The septaria in beds 6, 8, and 10 are much decomposed, and like 

 the clays in which they lie, they contain but few traces of fossils. 

 But those in 18, 20, 22, 24, 28, and 30 offer, in these respects, 

 marked contrasts. Externally they present much the same appear- 

 ance in size and shape. They are, however, more compact, and on 

 being fractured are found to contain a nucleus of claystone, which 

 has imbedded in it other small nodules, and the shells of Lima, 

 Plicahda, Pecten, Ostrea, and Avicula, many of which are often 

 invested in a pyritio matrix. 



The most marked feature in the section exposed in this pit is the 

 limestone course 25. It runs right across the face of this pit and 

 crops out again in the adjoining Glaisiers Pit. It immediately 

 overlies the " ferruginous nodular band," to which Mr. W. H. 

 Dalton refers when he says : " Both at Lincoln and Grantham, whilst 

 specimens of A. margaritatus have been obtained beneath this ferru- 

 ginous nodular band, no signs of that fossil were observed above 

 it, so it seems to form the upward local limit of the zone or range 

 of A. margaritatus.'" 



A. margaritatus occurs both in this limestone course and in the 

 overlying six feet of shales, clays, and septaria, so that, as far as 

 the Handley's Pit shows, the upwai'd limit of A. margaritatus is 

 eight feet above the " nodular band." ^ This limit is represented 

 by the band of septaria which is marked 16 in the section. The 

 limestone bed 25 is of a markedly argillaceous character. It is very 

 hard and compact, and varies in thickness from 1 ft. 6 in. to 2 ft. 

 Its fracture is very irregular, and, in places, it is frequently traversed 

 by minute veins of calcite that cut the rock in all directions, while 

 in others it contained masses of " dog-tooth " and " nail-head " 

 calc-spar. 



Its colour varies from a dark-grey to a light-blue, but after 



1 For the determination of the Foraminifera from these shales my thanks are due 

 to Mr. F. Chapman, F.E.M.S. 



2 My observations have been confirmed by the Rev. E. Nelson, who has also 

 collected A. margaritatus from bed 16 dowmvards. 



