﻿A. J. Jukes Broicne — On the Tipper Greensand, etc. 363 



this is not strictly true, because the former zone contains "beds of 

 Gault Clay which have never been included in the Upper Greensand. 

 The real fact is, that recent researches have shown the formations 

 known as Gault and Upper Greensand each to consist of two 

 divisions, but the lower part of the one being united palseonto- 

 logically with the upper member of the other, only three well- 

 marked groups can be established. Supposing, therefore, that the 

 names of Gault and Upper Greensand are still retained, we must 

 decide to which of the two this intermediate zone more probably 

 belongs, whether in fact we should extend the Greensand down- 

 ward or the Gault upward. I would advocate the latter measure, 

 and the restriction of the term Upper Greensand to the group of 

 beds containing a Warminster fauna ; with regard to stage B, 

 containing Ex. conica (the Ujoper Greensand of Mr. Meyer), I do 

 not think Dr. Barrels gives very strong reasons for classing it in 

 the lower division ; it is true that it does not contain many fossils, 

 and that these do not indicate any marked affinities, but the large 

 Janira ceqideostata is I think mostly found in the Warminster 

 beds ; its lithological constitution certainly links it rather with 

 the upper than the lower beds. I would suggest, therefore, that 

 the zone B of Ex. conica be included with the Warminster beds, 

 and that the limit of the lower division be placed at the shingle 

 beds in No. 4 of Mr. Meyer's section. The upper division would 

 then consist of two parts, zone of Pecten asper and zone of Ex. 

 conica, J)e Eance, the lower of which may be taken as forming the 

 base of the Uj^jDer Greensand. As a matter of fact this bed has 

 always been included in that formation, and it would cause great 

 confusion if in retaining the term we excluded this part of it ; the 

 twofold constitution of the Greensand is well seen at Wantage, 

 where, according to Mr, E. C. Davey, 30 feet of soft greensands are 

 underlaid by 6 feet of firestone. 



General Classification. 



i c Marl with small Brachiopods ) Feet 



Chalk Marl < b Zone of flocos. mceandroides > 40 — 80 



( a Glauconite (Chloritic) Marl ) 



Upper Greensand Warminster beds = zones of P. ^sj^.r and 



^^ ( Ex. conica (De Eance) ) 



Upper Gault { ^^-SeT ^"^' ''' ''"''^ ''^ Ammonites) ^^_^^^ 



Lower Gault \ ^'?^^^ °^ D'Orbigny = zones of Am. \ ,^q_^^^ 



\ laiitus ?ma Am. mterriiptus ) 



Lower Greensand j Aptien of D'Orbigny = zones of ^m. .««m- ) 

 I miUaris and J^ oikestone beds. \ 



The arrangement above suggested has also the merit of necessita- 

 ting only a very slight alteration in the lines on the published 

 Survey Maps, the term is rendered lithologically applicable, and a 

 definite fauma is secured to the formation instead of a mixture of 

 two different groups. It is true that the lists of UjDper Greensand 

 fossils will have to be revised, and those excluded which belong to 

 the lower zone ; but that was requisite in any case, and I venture to 

 hope that in the future care will be taken to indicate the exact 

 locality and horizon where any particular fossil or fossils are found. 



