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SUPPLEMENT TO THE BRITISH 



In 1852 we divided the Cretaceous System of Great Britain, according to the 

 ideas then prevalent, into Upper Chalk, Lower Chalk, Chalk-marl, Chloritic Marl, 

 Upper Greensand, Med Chalk, Speeton Clay, Gault, and Lower Greensand ; but a 

 comparison of our series with that which prevails upon the Continent made it soon 

 apparent that several subdivisions or beds, which occur in other countries, are 

 wanting in Great Britain. Geologists appear, however, unanimous in separating 

 the Cretaceous System into two great divisions ; the base of the Gault being considered 

 the line of demarcation dividing the upper from the lower portion of the system. 



The uppermost beds of the Cretaceous System, comprising the " Etage Garumnien " 

 of Leymerie, Pisolitic Limestone, Yellow Chalk of Maestricht, Limestone of Paxoe and 

 Limsteen, the Grey Chalk of Ciply, Limestone of Salthom, including M. Coquand's 

 " Etage Dordonien," and the upper part of the " Senonien" of D'Orbigny, as well as the 

 Limestone with Baculites of Valogne and the Chalk of Ignaberga, &c, appear to be 

 wanting in Great Britain. 



1. In England, in the descending series, we begin with the Upper or Norwich 

 Chalk, with Belemnitella mucronata, Ostrea vesicularis, Terebralula carnea, Mayas 

 numilus, &c. It represents M. Coquand's " Etage Campanien," and may be seen at 

 Norwich, Charlton, Antrim in Ireland, at Meudon, near Paris, and at many other 

 places. 



2. Lower Chalk (upper portion). — A Chalk much resembling the preceding, but 

 harder and usually known by the designation of " Chalk with flints." Among its 

 numerous fossils we may mention Micraster cor-anguinum and Terebralula semiglobosa. 

 It corresponds to the " Senonien " of D'Orbigny, " Santonien " of Coquand, and may be 

 seen at Lewes near Brighton, Dover, Hinton, and other places. Between this and the next 

 division there occurs upon the Continent several large deposits which are wanting in 

 England. 



3. Loiver Chalk (lower portion) with Micraster cor-testudinarium, having for its base 

 the zone of Ilolaster planus. This may be seen at Dover, near Lewes, &c. M. Hebert, 

 in a paper read before the Brighton Meeting of the British Association in August, 1872, 

 objected, with much reason, to the terms " Chalk with " and " without flints " being 

 made use of, from flints occurring both in the Upper and Lower Chalk. 



4. Chalk-marl, or Chalk with Lnoceramus labiatus. — This formation, which at 

 Watlington, Oxon, cannot be less than from fifty to sixty feet in thickness, occurs at 

 Glynde, near Lewes, and in other places. 



5. Upper Greensand. — This division should be subdivided, for it comprises several 

 important formations which have not yet been sufficiently defined, namely, the Chloritic 

 Marl of Chard, Chardstock, &c. ; the Greensand and Sandstone of Warminster ; Green- 

 sand of Cambridge (Upper Gault or "Etage Vraconien" of Swiss geologists). 



The " Hibernian Greensand " of Ireland is considered by Mr. R. Tate to represent 



