1864.] TATE CRETACEOUS ROCKS OF IRELAND. , 25 



Section in Colin Glen. 



g;^ White Limestone, resting on — 



P ^ Thickness, 



o _ r ft. in. 



■"S-d S 1- Compact dark chlorito-siliceous sandstone 6 6 



^ I § i 2. The same with Crustacea ( Callianassa, sp.) 3 



g^m 3. The same, but unfossiliferous, as No. 1 6 



^ , ^ r4. Yellow sandstone with nodular cherty masses, 

 -5 'a c J becoming blackish and shaly below, and yielding 



"" ' " I Pecten mqidcostatus, P. qiiadricostatus, and Ver- 



y micularia gidnquecarinata 30 



M 



PH 



s P^ 



3 ' 



Glauconitic Sands with Exogyra conica, &c 8 6 



54 



This section presents tlie maximum thickness attained by each 

 zone of the Hibernian Greensand. 



3. Upper Chalk. — a, Chloritic CTiaTk, or Basement-hed of the WTiite 

 Limestone. — The lithological characters and relative position of this 

 stratum have been abeady referred to. It is essentially a local 

 development, becoming attenuated tovs^ards the west, and at Cave 

 Hill is represented only by a bed otAmmchytes ovatus and a few Ven- 

 triculites interposed between the "WTiite Limestone and the Chloritic 

 Sandstone. It is entirely wanting further to the west, and then the 

 White Limestone rests abruptly upon the Hibernian series, whereas 

 in the eastern districts the Chloritic Chalk passes upwards into the 

 state of a white limestone, and downwards into that of a chloritic 

 sandstone. 



Its fossil contents are chiefly Sponges and Ananchytes ovatus. The 

 former characterize a distinct palaeontological zone reposing upon 

 that of the Ananchytes. 



"With Ananchytes ovatus, type, and A. gibbus, I foimd only Ga- 

 lerites albogalerus, type and tumid variety. 



In the Spongarian zone the following species are characteristic : — 

 Camerospongia fungiformis, Goldf., Ventriculites alternans, V. clecur- 

 rens, and Etheridgia mirabilis, spec. nov. 



b. White Limestone or Hard Chalk. — This stratum has been so 

 accurately described by previous writers that I need only repeat 

 their descriptions, so far as they are applicable to the stratum as 

 developed around Belfast. 



The rock is an imperfectly bedded white compact limestone, with 

 a splintery fracture, and containing layers of flints throughout. It 

 is overlain by the Basalt, and rests either upon the Chloritic Chalk or 

 the Hibernian Greensand ; from beyond CoHn Glen, by Kilcorig, near 

 Lisburn, to Moira, it is seen resting dii^ectly on the New Eed Marls. 

 It bears abundant evidences of alteration, namely, in its crystal- 

 line structure where in contact with the basaltic dykes, and in the 

 shattered condition of the flints in their vicinity. Furthermore, the 

 limestone is throughout the district capped by a layer of flints im- 

 bedded in an ochreous clay ; all these flints are of a deep bright-red 



