1864.J TATE CRETACEOUS EOCKS OF IRELAKD. 23 



arenaceous element prevails, and they assume the character of 

 yellow sandstones abounding in chert ; they are also comparatively 

 fossiliferous and of great thickness. The characteristic fossils of the 

 yellow sandstones of CoKn Glen, Black Mountain, &c., are, Ostrea 

 carinata, Pecten cequicostatus, P. quadricostatus, Rhynchonella latis- 

 siina, and Vermicularia quinquecarinata, E.oem. 



The argillaceous sandstones of Whitehead and Island Magee 

 contain in abundance Bitrupa deformis, Lamarck, Discoidea suh- 

 ucidus, Micrabacia coronula, and Vermictdaria qumquecarinata. 



c. The CMoritic Sands and Sandstones. — This division includes 

 part of the " Mulatto " of the workmen, and part of the '•' Chloritic 

 Chalk " of Portlock. Several authors have referred it to the Upper 

 Greensand. 



In the Woodburn section there is some slight evidence of un- 

 eonform ability between this zone and the underlying grey marls ; 

 that is to say, Bed No. 6 reposes upon a slightly undulated surface 

 of Bed No. 7 (see section, p. 21). 



The beds between the Grey Marls and the White Limestone are 

 generally siliceous sands in a calcareous paste, and contain dissemi- 

 nated chloritic grains. The compactness of this zone varies with 

 the locality. On the whole, I find that, in ascending the bed, it 

 becomes more and more compact, by the predominance of the cal- 

 careous paste, and the sihceous and chloritic elements become less 

 and less in amount, finally passing tip insensibly into the condition 

 of a white compact limestone. These general features are seen 

 especially in the eastern localities. 



Despite the greater or less uniformity in the lithological charac- 

 ters of this stratum, a study of the fossils has led me to refer the 

 upper portion of it, to which I apply the term " Chloritic Chalk," as 

 met with in the eastern escarpment of the Cretaceous area, to the 

 Upper Chalk. The band with Ananchytes ovatus I regard as the 

 lower limit of the Upper Chalk, though no line of demarcation exists 

 further than the appearance of the calcareous element in greater 

 force. In the Woodburn section (p. 21) it embraces Beds Nos. 2, 

 3, and 4. 



The relations of the Chloritic Chalk to the Chloritic Sandstones are 

 shown in the following sections, in which also is noted the local 

 variation in their composition. 



Section on the East Coast of Island Magee. 



Thickness. 

 ^ . f.2 1. White limestone. ft. in. 



cj^ J '^d r2. White limestone with chloritic grains increasing 



^§^g I^Ji downwards 1 10 



[ O ^ (_ 3. Ventriculite-bed ( Cephalites ficngiformis, &c.) 3 



g TJ f o r 



■g g I •■§ ^ I 4. Slightly compact green sands, witli Cyphosoma Cc- 



rs <u 



w^ ^ 



o 'q -j nomanense, Serpula jiliformis, Ostrea canalicidafa, 



&c. 



