Cycles of Sedimentation in the Eocene. 199 
IV. NOMENCLATURE. 
It may be useful to give here some reasons for the general names 
adopted for the cycles. i 
Landenian (Dumont, 1839, defined by Meugy, 1852)—The 
inapplicability of the terms Thanetian and Sparnacian have been 
mentioned above.” 
Ypresian (Dumont, 1849).—The term Londinian of Mayer-Hymar 
(1858) is bad, since he confused the London Clay and Woolwich 
Beds. Also confusion with Landenian in inevitable. Dollfus prefers 
his own term Cuisian (1880), on the grounds that Cuise is a more 
fossiliferous locality, and that neither stratigraphy nor paleontology 
is to be observed at Ypres. On the contrary, Ypres is a typical 
locality in that the beds are of the familiar argillaceous type, common 
to the Hampshire, London, and Belgian regions (London Clay). 
Marck, not very from far Ypres, Leriche has shown that the 
argillaceous sediments occur interbedded in certain localities with 
sands of Cuise type, and that the faunas of the London Clay and 
Cuise Sands occur in alternating layers. Moreover, fossiliferous 
horizons of London Clay species have recently been found in the 
Flanders plain round Ypres. 
Lutetian (de Lapparent, 1883) is generally accepted. 
Ledian (Mourlon & Vincent, 1887) was originally applied in 
Belgium to the beds with Nummulites variolarius. Auversian 
(Dollfus, 1880) was originally far more restricted in meaning. 
Bartonian (Mayer-Eymar, 1858).—Although a much misused term, 
the Barton sequence is a very good one to take as a type. 
V. CONCLUSION. 
This paper is a brief resumé of the results of several years field 
work on the Tertiary deposits. For the sake of brevity, references 
have been confined to a few special points. The author regrets that 
it is impossible, for the same reason, to acknowledge individually 
his indebtedness to a large number of friends both on the Continent 
and in England. Without their cordial assistance the work would 
have been “impossible. 
Part of the expense of this investigation has been defrayed by a 
grant from the Dixon Fund of the University of London, and by 
the Layton Research Studentship of King’s College (University of 
London). 
Postscript—(1) Belgian geologists have recently come to the 
conclusion that the Tuffeau de Ciply is not a lateral phase of the 
Calcaire de Mons, but is earlier (Danian) in age. 
1 Compare also Leriche, ‘‘ Observations sur la Classification des ‘Assises 
paléocénes et éocenes du Bassin de Paris’’?: Ann. Soc. géol. Nord, vol. xxxiv, 
1905, p. 383. Dollfus, ‘‘ On the Classification of the Beds of the Paris Basin ”’ 
Proc. Geol. Assoc., vol. xxi, 1909, p. 101. Lemoine, Géologie du Bassin de 
Paris, 1911, p. 198 et seq. 
2 See also Leriche, “‘ Surla signification des termes Landenien et Thanetien 
Ann. Soc. géol. Nord, vol. xxxiv, 1905, p. 201. 
” . 
i 
