36 Bulletin 15 346 



The Bourg limestone is the most important of the lower Oli- 

 gocene deposits of the Gironde valley. The depth varies from 

 I to 60 metres. Near Bordeaux it is quarried as a building stone. 



The fossils* are usually found only in casts. Some of the 

 more charadleristic are Ci^ejiaster IcEvis, Natica crassatina, N. 

 angustaia, Cerithium plicatum, C. h^ochleare, Ti'ochus Buchlandi 

 and Archiaclni armorica. 



Friable limestone of Agen. The friable limestone of Agen is 

 considered by M. Fallot as an eastern extension of the Bourg 

 limestone. 



Affinities of the Gironde Tqngrian fauna. As already noted, 

 the Tongrian fauna of the Gironde is more closely related to that 

 of the limestone of Rennes, in Brittany, than to any other deposit 

 in France. Its closest affinities are, however, with the Italian 

 fauna. 



Aqititanian. The upper Oligocene period (Aquitanian) in 

 southwestern France was charadlerized by changes in elevation 

 which resulted in alternate freshwater and marine deposits. The 

 fauna has been studied by Basterot,t Mayer, | Benoist,|| Degrange- 

 Touzin,§ Fallot and others.** The name Aquitanian was given 



* Fallot, Contr. a I'etude de I'etage tongrien, Mtm. Soc. Sci. phys. et 

 nat. de Bordeaux, t. 5, 1895. 



t Description geol. du bassin tertiaire au S. O. de la France, in-4°, 1825, 

 {Extrait des Mem. de la Soc. d^hist. nat. de Paris, t. 2, pt. i, 1825). 



X Description de coquilles fossils des terrains tertiaires inferieurs, Jotirn. 

 de Co7ic/i., 3enie ser., t. IV, p. 170, pi. 9; t. XII, pp. 168-181, 350-361, 1864; 

 Description de coquilles fossiles des etages superieurs des terr. tert., Ibid., 

 t. VII-X, XII, XIV, XVI, 1857-69. 



II Catalogue synonymique et raisonne Testaces Fossiles recueilles dans 

 les faluns miocenes des communes de La Brede et de Saucats, pp. 5-78, 

 265-460, Afies de la Soc. Linn, de Bord., 3eme ser., t. IX, 1873. 



\ Note sur deux affleurements de Falun situes dans le voisinage du 

 chateau du Thil. a Leognan ^Extrait des Pi-ocis-verbaux de la Soc. Linn, de 

 Bord., 4 dec, 1895; Les Scalariidse fossiles des Terrains Tert. sup. du Sud- 

 Ouest {Extr. des AEles de la Soc. Linn, de Bord., t. XLVIII). 



** Defrenoy et Elie de Beaumont, Fossiles des faluns de Saucats, Merig- 

 nac, Leognan, etc., Mem. pour servir a une desc. geol. de la France, t. Ill, 

 p. 118, 1836. 



Linder, Depots Lacustres du Vallon de Saucats, Comptes rendios de 

 ^excursion linniienne ii Saucats, 1869. 



Cossmann, Sur quelques formes nouvelles ou pen connues des faluns du 

 Bordelais, Ass.fran. pour P Avancemetit des Sci., 1894-5. 



