R. H. Rastall — Minerals of Lower Greensand. 211 



" It is difficult, owing to the small number of species collected, to 

 give a definite horizon. There are no specially characteristic species 

 contained, hut it is either Westphalian or possibly the Black Band 

 group of the Staffordian series which immediately overlies the 

 Westphalian. There is nothing in the collection to enable one to 

 decide this." 



EXPLANATION OF PLATE V. 



Slabs of clay-ironstone from the highest Coal-measures at Claxheugh, 

 co. Durham. 

 Fig. 1. — Surface with a number of individuals of " Aiicylus" Vinti, Kirkby. 

 Supposed to be the " spat " of Anthracomya Phillipsi (fide Herbert 

 Bolton). 



,, 2. — Ditto, the individuals more crowded together. 



,, 3. — A specimen of " Ancylus " Vinti, Kirkby, from slab (Fig. 1). x 5. 



,, 4. — Another specimen of same, from same slab, x 5. 



,, 5. — Slab covered with lamellibranchs. The largest specimens are 

 Anthracomya Phillipsi (Fig. 6) ; the smaller ones are A. minima, 

 Ludwig, the younger stage of A. Phillipsi. Some of these have 

 the umbones wrinkled and incompletely calcified, recalling 

 " Ancylus " Vinti. Specimens of A. vinti occur also on this slab. 



,, 6. — Anthracomya Phillipsi, from slab 5. x 4. 



,, 7. — Another younger specimen of same, ditto, x 4. 



III. — The Mineral Composition of the Lower Greensand Strata 

 of Eastern England. 



By K. H. Bastall, M.A., F.G.S. 



IK the ye#r 1913 the author formed the intention of carrying out 

 a comprehensive investigation of the mineral composition of the 

 Lower Greensand strata of England, in order to ascertain whether 

 any definite conclusions could be drawn as to the sources of the material 

 and the geographical conditions that existed while the deposits were 

 being formed. A large number of specimens were collected along the 

 outcrop from the Wash to the borders of Buckinghamshire and examined 

 by the usual laboratoiy methods. This work was interrupted by the 

 outbreak of war, and on returning to Cambridge after an absence of 

 nearly four years on Government service circumstances proved to be 

 unfavourable to a continuance of the work on the scale originally 

 contemplated. The district already dealt with forms in itself 

 a fairly well-defined unit, and it was decided to publish an account 

 of the results already attained, in the hope that they may be of 

 service to future workers in this interesting field of penological and 

 strati graphical research. 



Introduction. 



The formation generally known as the Lower Greensand attains 

 a considerable development in the eastern midland counties of 

 England. It has an almost continuous outcrop from the shores of 

 the Wash to the western borders of Bedfordshire, but further to the 

 west it is discontinuous and does not appear at the surface over long 

 stretches of country, being overlapped by the Gault. It is a question 

 still undecided whether it was ever deposited continuously in this 

 region and afterwards removed by inter-Cretaceous denudation, or 



