206 MIOCENE PERIOD. [Ch. XV. 



rium magnum, Mastodon angustidens, Hippopotamus major, 

 and PI. minutns, Rhinoceros leptorhinus, and R. minutus, Ta- 

 pir (jiyas, Anthracotherium (small species), Sus, Equus (small 

 species), Cervus, and an undetermined species of the Rodentia. 



The first species on this list is common to the Paris gypsum, 

 and is therefore an example of a land quadruped common to 

 the Miocene and Eocene formations, an exception perfectly in 

 harmony with the results obtained from the study of fossil 

 shells *. 



Basin of the Gironde and district of the Landes. A great 

 extent of country between the Pyrenees and the Gironde is 

 overspread by tertiary deposits which have been more par- 

 ticularly studied in the environs of Bordeaux and Dax, from 

 whence about 600 species of shells have been obtained. These 

 shells belong to the same type as those of Touraine. See Ap- 

 pendix I.f 



Most of the beds near Dax, whence these shells are pro- 

 cured,, consist of incoherent quartzose sand, mixed for the most 

 part with calcareous matter, which has often bound together 

 the sand into concretionary nodules. A great abundance 

 of fluviatile shells occur in many places intermixed with the 

 marine ; and in some localities microscopic shells are in great 

 profusion. 



The tertiary deposits in this part of France are often very 

 inconstant in their mineralogical character, yet admit generally 

 of being arranged in four groups, which are enumerated in the 

 explanation of diagram No. 51. 



In some places the united thickness of these groups is con- 

 siderable, but in the country between the Pyrenees and the 

 valley of the Adour around Dax, the disturbed secondary rocks 



* For further details respecting the basin of the Loire, see M. Desnoyers, Ann, 

 des Sci. Nat., tome xvi. pp. 1/1 and 402, where full references to other authors 

 are given. 



f M. de Bastcrot has given a description of more than 300 shells of Bordeaux 

 and Dax, and figures of the greater number of them. Mem. de la Soc. d'Hist. 

 Nat. de Paris, tome ii. 



