TERTIARY FOSSILS. 171 



the beds are seen dipping at an angle of 50° 

 to the west. The uppermost portion consists 

 of a bed of conglomerate, the pebbles in which 

 are limestone and serpentine. The inclined cliff 

 of scaglia, against which this conglomerate abuts, 

 is much water- worn and perforated by borers. 

 Beneath the conglomerate are sandy marls and 

 shales, about forty feet in thickness, containing 

 marine shells. These rest upon dark laminated 

 clays and marls, containing fossils in considerable 

 quantity. The width of the part of the valley 

 occupied by the tertiary is half a mile. 



Thirty-four species of mollusca were collected 

 in these beds, mostly in very good preservation. 

 Of these, twelve appear to be identical with, or 

 very closely allied to, Bourdeaux species. Three 

 or four are Italian species, described by Brocchi, 

 and not known in the French miocene. Two 

 are identical with Touraine fossils in Mr. Ly ell's 

 collection. Three have been recognized by 

 Signor Michelotti as Italian miocene species. 

 One is a Paris-basin shell, not known higher 

 up in the series. Four of the species, identical 

 with Bourdeaux forms, are supposed analogues 

 of Indian Ocean shells. The living analogue 

 of one of the fossils (a Pleuvotoma) identified 



