BINNIE: MESOZOIC ROCKS OF THE NORTH-EAST COAST OF IRELAND. 63 
Ceaomanien. Turonien. Senonien. 
Rhynchonella robusta 
,, Cuvieri 
Spondyliis spinosiis ..... ^ ,^ 
Cidaris subvesicularis . . ... ;u 
Ostrea columba ... si; 
„ semiplaiia ... ... 
He says lie has never seen in Ireland representatives of the 
Danien, all belong to the Norwich chalk. The chloritic beds he 
considers to be of tlie micraster age. He divides the chalk proper 
into two zones. (1) Marsupites; (2) Belemnitella. He says that 
the fauna and characters are similar to those of their English equiva- 
lents. (2) is thirty metres thick ; (1) is 4-5 metres. 
Comparison of the English and Irish Cretaceous. 
To account for the difference in character of the English and 
Irish faunas, M. Barrois supposes the latter to have been deposited in a 
shallow^ sea, proved by the glauconite bed and variable thickness. 
The denudation has been less than in England, only the upper 
beds were deposited, which were protected by the overlying basalt, 
and hence have a greater development than in England. 
The chalk is hardened or even converted into marble by dykes. 
The basalt consists of augitic lava flows, it occurs in three 
different forms, 1, the columnar ; 2, the spheroidal; 3, the amorphous. 
(1) The columnar consists of an aggregate of pillars, which 
may possess any number of sides from 4 up to about 12. They have 
the appearance of prismatic crystals, with the ends rounded into 
either a cup or a hemisphere. Each pillar consists of a collection of 
these prisms, each standing on the top of the other, the faces of the 
Ireland. England. 
Metres. 
a. White Chalk with flints 20-30 .. Belemnitella mucronata 
h. „ „ „ 4- .5... Marsupites 
France. 
