OF THE PARIS BASIN. 43 



locality Ormoy-la-Riviere, south of Etampes. The only two 

 fossiliferous localities in these beds are at Ormoy and Chalo-Saint- 

 Mars. We visited the former place, but no good section was 

 visible ; a few lumps of stone and a dirty grey sand occurred on 

 the edge of a ploughed field high on the hill to the east of the 

 village, and here and there the characteristic fossil, Cardita Bazim, 

 and others put in an appearance, but that was all. The Ormoy 

 beds in their unfossiliferous condition, however, are extremely 

 easy to study in the locality, owing to the numerous quarries in 

 them for building stone. Perhaps the finest section is the one we 

 saw at C6te-.St.-Martin, where the overlying beds are also well 

 developed. Other exposures are at St. Hilaire, Valnay, Lardy, 

 Bouray, La Ferte-Alais and Maisse. In certain places the 

 uppermost beds are of fluviatile origin, which, together with the 

 palcxontological evidence, is an indication of the close affinities 

 subsisting between this horizon and the Beauce limestone, 

 presently to be described ; in other words, it attests the inti- 

 mate relationships of the Tongrian with the Aquitanian. We 

 would especially draw attention to this fact as showing the 

 complete succession of this important phase of the Oligocenes in 

 the vicinity of Etampes, and its bearings on the general question 

 of the sub-division of this part of the European Tertiaries. That 

 the line can easily be drawn between the Tongrian and A([uitanian 

 beds in other Tertiary basins we freely admit, but the division 

 seems very arbitrary so far as the Paris basin is concerned. 



11. MARLS OF ETAMPES. 



Above the Ormoy sand and sandstone comes the local horizon 

 known as the Bithiuia-xn'^xh of Etampes. It is essentially a 

 passage bed, containing Limncea, F/a/wrlns, Fi/pa, Helix and 

 certain plants ( C/z^n? inedicaginula, for example), and it is covered 

 by the formation next described. 



12. LIMESTONE OF BEAUCE. 



These beds are sometimes known as the " T?-avcrti/i de Beauce,^'' 

 or " Tr avert i)i super ieur." 



As the Beauce Limestone is traced northwards from the typical 

 locality it becomes much altered in character, and is then called 

 the " Meiilieres de Montmorency. " These vieulieres are well 

 developed on the plateaux round Paris where the lower portions 

 are sometimes fossiliferous, containing Potatnidts, &c. Helix 

 Ramondi has been found at Trappes*, whilst M. Dollfus has 

 detected Valvata disjuncta at Frepillon. This latter authority 

 saysf that the Beauce Limestone, taken together with its altered 

 facies the " Meiilieres de Montmorency" covers the greater part 



* Tournouer, Bull. Soc. Gcol. Fr., 2e. ser., t. xxiv. (1867), p. 489. 



t Dollfus, Extension dcs tcrr. Tert. bas. Anglo-Pariskn, Mem. Soc. Geol. Norm." 

 Comptcs rcndus, Exp. (1877), p. iS. 



