Parr IIL, Snor. iii. § 2.) CRETACEOUS. 819 
7. Dark clay (6ft. 2in.) highly fossiliferous, with Ammonites auritus, 
Nucula bivirgata, N. ornatissima, Aporrhais Purkinsoni, Fusus inde- 
cisus, Pteroceras bicarinatum. 
. Dark mottled clay (1ft.), Ammonites denarius, A. cornutus, Turrilites 
hugardianus, Necrocarcinus Bechet. 
. Dark spotted clay (1ft. 6in.), Ammonites lautus, Astarte dupiniana, 
Solarium moniliferum, Phasianella ervyna, numerous corals. 
. Paler clay (4in.), Ammonites Delaruei, Natica obliqua, Dentalium 
decussatum, Fusus gaultinus. 
. Light fawn-coloured clay, “ crab-bed” (4ft. 6in.), with numerous cara- 
paces of crustaceans (Palzocorystes Stokesti, P. Broderipti), Pinna 
tetragona, Hamites attenuatus. 
2. Dark clay marked by the rich colour of its fossils (4ft. 3in.), Ammonites 
auritus, Turrilites elegans, Ancyloceras spinigerum, Aporrhais calca- 
rata, Fusus itiertanus, Cerithium trimonile, Corbula gaultina, Polli- 
cipes rigidus. 
1. Dark clay, dark greensand, and pyritous nodules (10ft. lin.), Ammo- 
\ nites interruptus, Crioceras astierianum, Hamites rotundus. 
Lower Greensand. 
Lower Gault. 
a a et ee 
Oo Pm oT oO 
Mr. Price remarks that out of 240 species of fossils collected by him 
from the Gault only 39 are common to the lower and upper divisions, 
while 124 never pass up from the lower, and 59 appear only in the upper. 
The lower Gault seems to have been deposited in a sea specially favour- 
able to the spread of gasteropods, of which 46 species occur in that divi- 
sion of the formation. Of these only six appear to have survived into 
the period of the upper Gault, where they are associated with five new 
forms. Of the lamellibranch fauna, numbering in all 73 species, 39 are 
confined to the lower division, four are peculiar to the passage-bed 
(No. 8), 14 pass up into the upper division, where they are accompanied 
by 16 new forms.t About 46 per cent. of the Gault fauna pass up into 
the upper Greensand. 
Cenomanian.*—Under the name of Upper Greensand have been 
comprised sandy strata, often greenish in colour, which are now known 
to belong to different horizons of the Cretaceous series. If the term is to 
be retained at all, its use must be accompanied with some paleonto- 
logical indication of the true position of the beds to which it is applied. 
According to the recent researches of Dr. C. Barrois the English green- 
sand, as originally defined by Berger, Inglefield, Webster, Fitton, and 
others, has no such distinct assemblage of fossils as might have been 
supposed from its lithological characters, but appears to be everywhere 
divisible into two groups, a lower containing Ammonites rostratus (inflatus), 
2 @).). Geol. Soc. xxx. p.. 390. 
2 Within the last few years the old lithological subdivisions of the English Upper 
Cretaceous beds have been found to be wanting in paleontological precision, and are 
gradually being supplanted by the terms already proposed by D’Orbigny, which have 
Jong been in use in France. These terms are here employed, but their equivalents in 
the old nomenclature will be understood from the table on p. 815. To M. Hébert 
geology is mainly indebted for the thorough detailed study and classification to which 
the upper Cretaceous formations of the Anglo-Parisian basin have been subjected. In 
1874 he published a short memoir in which the chalk in Kent was subdivided into zones 
equivalent to those in the Paris basin (Bull. Soc. Géol. France, 1874, p. 416). Subse- 
quently the same task was taken up and extended over the rest of the English Cretaceous 
districts, by Dr. Charles Barrois (“ Recherches sur le Terrain Crétacé Supérieur de 
Angleterre et de ’Inlande.” Lille, 1876). The first English geologist who appears to 
have attempted the paleontological subdivision of the chalk was Mr. Caleb Williams 
(Lewes, 8vo, 1870. . or the Geologists’ Association). See also W. Whitaker, “ Geology 
of the London Basin,” Geol. Survey Memoirs, vol. iv., and authors there cited, A 
tolerably full bibliography will be found in Dr, Barrois’ volume. i 9 
vo G 
