Yol. 52.] A DELIMITATION OF THE CENOMANIAN. 123 



rough or gritty to the touch, and it contains less glauconite than 

 that below. 



Grey or black cherts in separated nodules continue to occur either 

 scattered through the chalk or in lines at irregular intervals. 



The bluish colour, probably due to argillaceous matter deposited 

 with the chalk, gives place very irregularly to the yellowish-grey 

 which is the characteristic tint of the French Cenomanian. Some- 

 times it extends up for 12 or 14 feet above the basement-bed, some- 

 times only 3 or 4 feet, and in one section near Havre the colour does 

 not reach the Chloritic Marl. 



St. Jouin. 



In going to the eastward some of the features just described as 

 occurring at the base of the Cenomanian become lost, and the section 

 seen at St. Jouin is somewhat different from that at La Heve. The 

 Chloritic Marl, with the brown sandy seam and phosphates, is the 

 same, but the succeeding siliceous beds have died out and are re- 

 placed by yellowish-white chalk containing comparatively little 

 glauconite, and in this are lines of thin-skinned black cherts. Above 

 this the rock for a short distance has a bluish cast. 



Near the top of Bed 6 there comes in a course of grey gritty 

 limestone, with green-coated nodules, much resembling the Tot- 

 ternhoe Stone of Norfolk and Suffolk. Still farther east, at Brunval, 

 this bed thickens and is divided into two layers, separated by 

 grey, glauconitic, gritty chalk. A marked bed of massive chert 

 immediately beneath this can be followed by the eye from St. Jouin 

 to Brunval. 



This hard bed thins to the westward and is lost before Cape 

 La Heve is reached. We believe, however, that the massive chert- 

 bed which just underlies it is at about the same horizon as the 

 five massive chert-beds at La Heve. 



M. Lennier has minutely described the section seen at St. Jouin 

 in an account published in 1884 of an excursion of the Societe 

 Geologique de Normandie to St. Jouin, Brunval, and Antifer. He 

 makes the thickness of the Cenomanian at this point to be 118 feet 

 7 inches, which nearly coincides with our own measurement of 

 119 feet 6 inches. But his section does not appear to include the 

 basement-bed, so that, if this Be added, his estimate will be somewhat 

 greater than ours. "We here tabulate for comparison the section of 

 St. Jouin as taken by M. Lennier and ourselves, some of Lennier's 

 beds being grouped to save space. 



