Land-tracts during the Secondary and Tertiary Periods. 275 



and which in India bounded this gulf on the south, we have the 

 nummulitic eocene beds of Cutch similarly connected with the 

 fluviatile deposits intercalated with trap which occupy a con- 

 siderable area in Western India. There seems to me every 

 reason to infer that the suggestion of M. d'Archiac, quoted by 

 Sir Roderick Murchison*, affords the true explanation of the 

 phenomena presented, viz. that the eocene formations of Western 

 Europe were but the littoral deposits of the great nummulitic 

 gulf-j-j and were formed by the sand and mud of rivers debouch- 

 ing into the gulf at the spots where these formations occur, the 

 deltas of which rivers have furnished the estuarine and fluviatile 

 beds which are associated with these deposits. The mollusca 

 of the eocene formations of England, France, and Belgium ap- 

 pear \ to have all their affinities with the existing mollusca of the 

 present Eastern seas (being those to which we trace the junction 

 of the nummulitic gulf), but exhibit a dissimilarity to the 

 mollusca of the eocene formations of America. M. Abich, in his 

 ( Palaeontology of Asiatic Russia ' (Mem. de VAcademie des 

 Sciences de St. Petersbourg, 6 me serie, vol. vii.), figures thirty-two 

 eocene species of mollusca, of which twenty-six are, he considers, 

 identical with English, French, and Belgian eocene forms, two 

 are given by him as indeterminate, and four only as new species, 

 being respectively 81 "25, 6*25, and 12*5 per cent, on the whole 

 number of species described by him. These fossils, obtained 

 from beds reposing on nummulitic rock and overlain by middle 

 tertiary in the neighbourhood of the Sea of Aral, a district con- 

 tiguous to the southern extremity of the Oural region (which 

 formed the land fringing the sea these forms inhabited), lived at 

 a distance from the English, Belgian^ and French basins of up- 

 wards of 2500 miles, and strongly confirm the inference (arising 

 from the outcrop across Russia of older strata uncovered by eocene) 

 of a continuous coast-line joining these distant places, lying as 



found. Similar fluviatile and estuarine deposits will doubtless hereafter be 

 discovered associated with the eocene beds of the Aral Sea and Araxes, 

 The return of the sea after the long intra-cretaceous interval to parts of 

 its old secondary bed appears to have been very gradual, and the formation 

 of the great nummulitic deposit to have been preceded by local tertiary 

 formations, mostly fluviatile and estuarine. This, at least, was the case 

 according to M. d'Archiac (An. Foss. de VInde, p. 77) ; his remark, how- 

 ever, admits of many exceptions, as the nummulitic deposits frequently 

 repose immediately on the secondaries or other older rocks. 



* Quart. Journ. Geol. Soc. vol. v. p. 301. 



t MM. Hebert and Renesier also (Bull. vol. xi. p. (504) regard their upper 

 division of the nummulitic deposit of the Alps as the marine equivalent of 

 the upper eocene of the Paris basin, and probably also of the oldest mio- 

 cene (Mayence, Limbourg, Sables de Fontainebleau, &c). 



X See Introduction to Eocene Bivalves, p. 10; Palseontographical Society's 

 Volume for 1859. 



