34 EELIQUI^E AQUTTANKLE. 



The outcropping edges of these Upper Limestones follow an irregular line crossing the lower part of the 

 Vezere. They have been very much denuded, and in some places have been cut away by the valleys so as 

 to expose the next underlying set of beds. In the gorges of the Cretaceous Limestone near Campagne, 

 north-west of St.-Cyprien, even the Jurassic series, characterized by Exogyra virgula, is exposed. 



Deuxieme Etage. The next lowest Cretaceous zone consists of grey or whitish, marly, chalk-like limestone, 

 in some places full of nodules of Flint. This band also traverses the Departments du Lot, de la Dordogne, 

 and of the two Charentes, passing southwards under the yellow limestones, and on the north and east resting 

 on an underlying white limestone. Towards its base the marly chalk, or chalk-marl, is sandy, glauconitic, 

 hard, and laminated ; but upwards it becomes thick-bedded, sandy, glauconitic, and micaceous, with grey 

 and black flint-nodules distributed unequally throughout ; and in its uppermost part this chalk is still more 

 marly, friable, and soft, with fewer green glauconitic grains. Some of the most characteristic of the fossils 

 of this " grey chalk " are Ostrea proboscidea and 0. auricularis. The lower beds are especially rich in 

 fossils, comprising numerous Polyzoa, Ammonites and other Shells, Echinoderms, claws of a Hermitcrab, 

 Fish-teeth, &c. 



This marly stratified limestone forms the banks of the Vezere at Montignac*, where it is characterized by 

 Terebratula alata, Lima Santonensis, and Pecten quadricostatus, and contains also, besides other fossils, 

 Hippurites organizans, Sphcerulites Sawvagesii, ifec. The general dip of the beds here is, according to 

 M. Harle, not more than 2-2 in 100 to the W. 25 S. 



Beyond the neighbourhood of Montignac to the north-west, this second zone is more outspread, parti- 

 cularly on the Manoir and the Isle Eivers ; and it is thicker and better stratified, yielding a good building- 

 stone, on the Isle, where the beds are 90 metres thick ; and at Perigueux they are over 120 metres, with 

 black flint in abundance. 



Troisieme Etage. The third group of limestones, forming the uppermost member of the Lower Cre- 

 taceous Formation, consists of: 1st (uppermost). Whitish limestones (white to the east, but yellowish 

 westward), sometimes compact and subcrystallinef, sometimes soft and very friable, and nearly always 

 abounding with Rudistes (Radiolites lumbricalis, E. angulosus, R. cornu-pastoris, SpTicerulites Ponsianus, and 

 Sph. Beaumontii), and constituting M. d'Archiac's "Middle Eudistes-zone." 2nd. "White, greyish, and 

 yellowish marly limestones. 3rd. Yellowish marly limestones, sandy and glauconitic, containing Ammonites 

 Fleuriausianus &c., and blue clays with many Oyster-like Shells (such as Ostrea biauriculata and Exogyra 

 eolumba). 



* The overlying limestone at Montignac (referred to also at page 32) is regarded by M. Harle as being 

 really a portion of the " Second Stage," and not an eastward extension of the " First Stage," reaching to 

 Sarlat, as M. d'Archiac described it. M. Harle traces it from Gourdon, &c., as a yellowish and glauconitic 

 limestone, more thickly developed around Sarlat than it is even at Perigueux, where it is micaceous. It is 

 composed of fragments of Shells and Polyzoans, with a yellowish calcareous cement. It usually resembles in 

 colour and general appearance the " Upper Yellow Limestones ; " but it really lies under thn friable chalk- 

 marl and upon the very persistent grey marly strata (at about 70 metres above the level of the valley at 

 Montignac) ; and all these together constitute the base of M. d'Archiac's ' Deuxieme Etage,' and of the 

 Upper Cretaceous Formation. (Harle, ' Bullet. Soc. Geol. France,' Deux. Ser. vol. xix. pp. 120 ifec.) 



t Locally termed " Chaudron." It is characterized by Sphcerulites radiosus, Sph. Sauvagesii, Hippurites 

 organizaiis, and H. comu-vaccinum. 



