158 



Passing the disturbed beds, strata of calcareous rock, more or less 

 argillaceous or arenaceous, alternating with a bluish clay or marl, 

 rise regularly at an angle of 60° or 70°, and are continuous for 

 nearly a mile, forming cliffs above 120 feet high. The uppermost 

 of these bed's is chiefly composed of nummulites and lenticulites, the 

 arenaceous strata contain numerous and well-preserved corals, the 

 species of which have not as yet been determined, though referred 

 by D'Archiac to cretaceous forms. In the lower beds the best iden- 

 tified tertiary forms were found mingled with species hitherto re- 

 garded as cretaceous, such as Serpula ampullacea and S. rotula. 

 Among the moUusca occurred Spondylus rarispina, Ostrcea spathu- 

 lata, Dentalium grande, Turritella cariniferaj Scalaria semicostata and 

 acuta, Cerithium turritellatiim and cinctum, with several undetermined 

 species of various genera. 



The cliffs cease for a quarter of a mile, being terminated by a 

 fault, when the strata again rise at a small angle in the same direc- 

 tion. Their mineralogical character however is different, as they 

 consist of a marly light-coloured limestone, abounding in fossils 

 which are mostly distinct from those of the preceding beds, with 

 the exception of the corals. The protrusion of igneous rocks has 

 changed this limestone in places into a hard crystalline marble 

 or dolomite. In this part of the series were found Terehratnla bisi- 

 nuata and striatula. Another fault throws these beds beneath the 

 shore, and at an interval of a few hundred yards they are succeeded 

 by a series of cretaceous beds resembling chalk marl, the general 

 inclination and direction of which, on account of frequent disturb- 

 ances, are difficidt to determine, but appear to be the same with 

 the last-mentioned strata. The cliffs formed by the cretaceous 

 strata rise to a height of from 50 to 150 feet. Three or four species 

 of Nautilus and Ammonite, and a few bivalves, chiefly Inoceramus 

 Cuvieri, are found in them, but there is no fossil common to the beds 

 separated by the last-mentioned fault. 



The beds overlying these undoubted cretaceous strata have been re- 

 ferred by the French geologists, quoted by Mr. Pratt, to the upper 

 part of the cretaceous system, both on account of the superposition 

 and direction of the strata and of the contained fossils, which they 

 regard as cretaceous species. But a closer examination of the or- 

 ganic remains shows that such as may be identified with known 

 species are mostly tertiary forms, while such as appear to be creta- 

 ceous, belong to genera and species of variable and uncertain cha- 

 racter. The Echinodermata, as identified by Dr. Grateloup, do not 

 agree with the references, except one, which is a tertiary species. 

 The variation in the mineralogical character of the beds sufficiently 

 accounts for the gradual change of species observed from the first 

 rise of the strata to their termination. Certain species were common 

 to all the beds preceding the second fault. The deposit is appa- 

 rently covered in its upper part by the plastic clay, to which it 

 approaches nearest in mineralogical character. At Dax and at 

 Royan similar deposits under similar circumstances were observed 

 by Mr. Pratt. 



