306 A. J. Jukes-Browiie — Ttco Stages in Upper Cluilk. 



this zone, as developed in Hampshire/ into three sub-zones, viz. : 

 (1) a sub-zone of Echinoconis scutatus, var. depressa, (2) a sub-zone 

 of 0. pilula, and (3) a sub-zone of A. quadratus. Mr. Brydone 

 informs me, however, that he has since come to the conclusion that 

 it will be better to make two distinct zones out of this great 

 thickness of chalk, a lower zone of 0. pilula and an upper one of 

 A. quadratus. This proposal has the advantage of agreeiuji' with the 

 zonal divisions adopted in Germany, where this portion of the Chalk 

 has been divided by Schliiter into a lower zone of Scaphites hinodosus 

 and a higher one of A. quadratus} 



In France also two zones have been recognized in this part of the 

 Chalk ; by J. Lambert in the Department of the Yonne, by A. Peron 

 in the vicinity of Reims and Epernay, and in A(juitaine by Arnaud. 



In the Yonne a series of zones was established by Lambert ^ and 

 indicated by letters, his zone M being about 100 feet thick and 

 corresponding with the 0. pilula zone of Mr. Brydone, for it is 

 characterized by the abundance of 0. pilula with what is now 

 known as A. gramdatus. His zone N, about 130 feet thick, corre- 

 sponds roughly with that of A. qxiadratus, its special fossils being 

 A. quadratus, Offasfer corculum, and Micraster Schroder i ( = M. glyphus 

 in Lambert's papers). 



The same two zones can be i-ecognized in the JiLarne near Reims 

 where A. Peron* has sliown that the ' craie k A. quadratus' is 

 divisible into two zones, a lower one characterized by Micraster 

 gilbus, var. fastigatus, Gtiuthier. and an upper one with M. glyphus 

 (= Schroderi) and Salenia Heherti. Ojfaster pilula is also conmion in 

 the lower zone and rare in the upper. h\ Aquitaine a similar 

 succession of zones has been established by H. Arnaud,^ and lettered 

 in a similar manner from A to S. Of these the zone P' (= that of 

 0. pilula) is characterized by the occurrence of Micraster regularis, 

 Echinocorys orbis, and Pyrina petrocoriensis, and M. de Gi'ossouvre has 

 shown tliat its special Ammonite is Elacetiticeras bidorsatum. The 

 zone P^ (= that of A. quadratus) is a sandj^ chalk with few fossils 

 except bands of Ostrea vesicularis, but examples of A. quadratus and 

 Mortoniceras delaicarense have been found in it. 



From these observations it is clear that both in the South of England, 

 the North of France, and in Aquitaine, the mass of chalk which lies 

 between the zone of Marstipites and the Chalk containing^. miicro7iata 

 is divisible into two distinct zones which are recognizable by the 

 occurrence of certain species of Echiuoderms and Belemnites, apart 

 from the rarer occurrence of Ammonoids. Thus, if the zone of 



' Tlie Zones of the Chalk in Hants, by C. Griffith & E. M. Brydone 

 (Dulau & Co., 1911), pp. 3, 10. 



• See Schliiter in Zeitsch. dcr Deutsch. Geol. OesellscJiaft , Bd. xxviii, p. 457, 

 1876, and Imp. Geol. Inst., Vienna, Sitz. for 1877. 



* Lambert, " Terrain Cretace du depart, de I'Yonne " : Bull. Soe. Sci. hist, et 

 nat. de I'Yonne for 1876. 



■* Peron, " Terrain de craie dans le Sud-est du bassin angloparisien " : op. cit. 

 supra (1887). 



^ " Le Terr. Cret. du Sud-ouest," Mem. Soe. geol. France (1877); and 

 " Eeport of Excursion to the Charente ", Bull. Soe. geol. France (1877). 



