116 Belemnitella Americana and Mucronata [314 



localities in west France, in Charente, these two basins form- 

 ing the legs of a triangle; and finally, eastward from the 

 southern limit of this trough, across the present site of the 

 Alps, connecting the two legs of the triangle is a subordinate 

 basin, in which marls and limestones were deposited, connect- 

 ing with the basin of Eussia. 



This rough triangle around Germany left the greater part 

 of the German Empire above water during late Senonian 

 time. A. E. Wallace (15, p. 91) quotes Sir Charles Lyell as 

 follows, "pure chalk, of nearly uniform aspect and compo- 

 sition is met with in a northwest and southeast direction, 

 from the north of Ireland to the Crimea, a distance of about 

 1140 geographical miles; and in an opposite direction it 

 extends from the south of Sweden to the south of Bordeaux, 

 a distance of about 840 geographical miles." Wallace goes 

 on to say that, while this marks the extreme limits within 

 which true chalk is found, "the chalk is by no means con- 

 tinuous. It probably implies, however, the existence across 

 central Europe of a sea somewhat larger than the Mediter- 

 ranean." 



The most widespread and the most typical chalks of Upper 

 Cretaceous age are those represented by the Upper Chalk of 

 England, and its equivalents, the Campanian and Maestricht- 

 ian, of the continent. In northeastern Ireland, in Antrim, 

 under a Tertiary basaltic flow, resting uncomformably on 

 Liassic and Ehaetic strata, Jukes-Brown (11, p. 322) gives 

 the following series, all of Upper Chalk age: 



3. White limestone, with B. mucronata 100 ft. 



2. Hard, pinkish, glauconitic limestone, with quartz 



grains, and phosphatic nodules 4 ft 



1. Glauconitic limestone, passing down into glauconitic 



sand 16 ft. 



Geikie (12, p. 1194) refers to this series as "Hard white 

 chalk, 65 to 200 feet, with Echinocorys [Ananchytes] sul- 

 catus, etc. = Zone of B. mucronata." Very little referable 

 to the Upper Chalk remains in Scotland, but in the west, 

 under the volcanic plateaus of Mull and Morven, some of the 



