280 
CONCLUSION. 
proper, the more so as they have been found both on the northern flanks of the 
Caucasus and in the Crimsea, where the whole Cretaceous system, from the Neoco- 
mian to the upper chalk and from the latter to Nummulitic strata, with shells of 
tertiary age, has been fully described by M. Dubois 1 and M. Huot 2 . 
It has been stated by us, that we cannot truly recognize in the ascending order 
an upper greensand on which the white chalk rests. On the contrary, where we 
saw the white chalk thinning out amid other strata, the beds which most resemble 
the “ planer kalk ” of Germany or the malm rock of England, and which at Kursk 
contain Terebratulse and a Belemnite, lie above and not below it. These litholo- 
gical discrepancies are, how T ever, no greater than those which exist in the distribu- 
tion of the different members of the system wdien followed from England to Eastern 
Germany, or from the north to the south of France, whilst the organic remains 
assure us, that all these deposits belong to one natural system. 
The distribution of certain types of animal life through varied and distant 
masses of inorganic matter, is doubtless of great geological interest, and compels us 
to be cautious in not attaching too much weight to mere details of mineral sequence. 
At the same time it appears, that mineral characters, under the limitations which 
we have endeavoured to define, are not to be neglected even in geological classi- 
fication ; for we have ascertained, that in the remotest regions of the Volga, green- 
sand, ironsand, chalk and chalk marl occur, in which the same group of fossils 
prevails, as in rocks of Britain and France which hold the same relative place in geo- 
logical succession ; and we have shown the extension, at intervals, of pure white 
chalk containing some characteristic organic remains, from the British Isles to the 
confines of Asia. 
Doubtless, therefore, these facts demonstrate, that during the cretaceous as in all 
the preceding geological epochs, there existed a most widely-spread diffusion of 
similar agencies which produced this general uniformity of result. 
1 Consult the letters of M. Dubois de Montpereux to M. Elie de Beaumont ; Bull, de la Soc. Geol. de 
France, vol. viii. p. 371 ; and his Table, ib. p. 385. Also the great work of the same author. Voyage en 
Caucase, en Armenie, en Crimee, &c. ; and see particularly Serie V. and VI. pi. 13 and 14 ; where the 
Neocomian and chalk formations are given in detailed sections. The last eighteen plates of the fifth series 
oiler a complete resume of the geological history of the Crima;a. 
4 Voyage dans la Russie M eridionale et la Crimee sous la direction de M. A. Demidoff, vol. ii. p. 398 ; 
Partie Geologique de M. Huot. This author divides the Cretaceous system of the Crimsea into three 
stages, Neocomian, greensand and chalk, classing the overlying Nummulitic beds as tertiary, a point to 
which allusion will be made in the next chapter. 
N.B. Erratum. — For Inoceramus crista galli, p. 266, read Ostrea crista galli, and for Frondicularia com- 
planata, p. 273, read Ananchytes ovata. 
