118 A DELIMITATION OF THE CENOMANIAN*. [May 1 896. 



Like the pebbly sand, these beds diminish westward; for 

 just south of the lighthouses the thickness of Gault and Gaize is 

 28 feet. M. Lennier gives the thickness of the Gault at Cauville, 

 .some 6 or 7 miles north-east of Cape La Heve, as 22-23 feet, and he 

 divides it into three beds. 1 Here therefore the combined thickness 

 of Gault and Gaize is probably about 50 feet. 



Prof. Hebert 2 was of opinion that no actual representative of the 

 Gault occurs at La Heve. He refers to its existence at Cauville, 

 and states that common Gault fossils were there abundant and well- 

 preserved. He also admits its occurrence near Octeville, where 

 * the bed of conglomerate is covered by a blue clay without glau- 

 conite, but containing many small pebbles of quartz and septaria, 

 with Gault fossils.' 



' At Cape La Heve/ he says, ' this bed is only represented by a 

 layer of septaria, of pebbles, of vegetable fragments, or of fossils 

 of the Gault, washed by the waters which brought the glauconite, 

 and remanies in the midst, and especially at the bottom of this 

 deposit, in contact with the conglomerate.' This appears to be a 

 description of the basal nodule-bed; these 'septaria' are doubt- 

 less what we have called phosphate-nodules. 



He continues as follows : — ' Je range dans cette derniere assise 

 (Craie glauconieuse) les argiles noiratres, tres glauconieuses, avec lits 

 siliceux intercales, qui, au Cap La Heve, reposent immediatement sur 

 le poudingue a Ostrea aquila ; ' and he gives the thickness of these 

 beds as from 16 to 20 metres (i.e., 52 to 66 feet). This great 

 thickness suggests to us that Prof. Hebert may have included in 

 this division of the Craie glauconieuse all the beds which have a 

 blue-grey colour, for our measurements make them 52 to 55 feet. 

 This view receives some confirmation from his further remarks, 

 which are : — ' It is true that there occur in this series a certain 

 number of Gault species, whose existence I do not deny, but these 

 beds also yield a good number of the more characteristic species of 

 the Craie glauconieuse: among Echinoderms, Epiaster crassissimus, 

 Epiaster distinctus, Holaster suborbicularis, Cardiaster bicarinatus, 

 which abound, the last especially, in one of the siliceous beds ; 

 among the Acephala, Pahopcea mandibula, Ostrea conica, etc. It is 

 this lower series that I have designated by the names of the zone 

 of Holaster suborbicularis and Ammonites inflatus.' 



Of the echinodermata mentioned above we found only Epiaster 

 crassissimus, and that is common above bed 5. We did not find 

 any below, and even if they did occur we cannot regard that fact as 

 very significant. There is no doubt that our bed 4 belongs to the 

 zone of Ammonites inflatus, but both M. Lennier and Prof, de 

 Lapparent exclude that zone from the Cenomanian ; and we are 

 entirely of their opinion on this point. 



Being familiar with the lithological change which our Gault 

 exhibits as it is traced westward, we see no reason for consider- 

 ing the Gault to be absent because the clay which occupies its 



1 Bull. Soc. Geol. Norm. vol. vi. (1880) p. 358. 



2 Bull. Soc. Geol. France, ser. 3, vol. iii. (1875) p. 516. 



