The Cretaceous Strata of County Antrim. 13l 



conglomeratic bed. — (d) The Peninsular Division. In the uorthern 

 portion of county Antrim, the highest zones of the White Chalk rest 

 on Archrean, Carboniferous, and Triassic rocks (which must have 

 formed a peninsula or insular area in the Cretaceous sea), the basal 

 conglomeratic bed being well marked, and old Cretaceous beaches 

 preserved. — Finally (e) The Northern Division. This occupies a 

 strip on the northern and north-eastern shores, and includes Bathlin 

 Island. The lower beds are only feebly developed, while the three 

 highest zones of the White Limestone (BelemniteUa vera to B. mucro- 

 natci) attain a great thickness, and are very pure chalk-beds. Taking 

 the various divisions together, it is concluded that Divisions b, c, 

 and e first underwent depression, area b being nearest to the shore- 

 line, Divisions a and d being higher ground, and only becoming sub- 

 merged at a late period in tipper Chalk times. 



II. Chemical and Micromineralogical examination of the litho- 

 logical types. — The Glauconitic Hands are characterized by the 

 abundance of glauconite (23 c / o CaC0 3 ), showing evidence of having 

 been formed in the interior of foraminiferal shells; the Glauco- 

 nitic Marls by an abundance of spheres and rods of pyrites ; the 

 Yellow Sandstones by a series of heavy minerals, notably 

 rutile, zircon, tourmaline, kyanite, and perfectly-formed crystals of 

 garnet: the Inoeeramus-zone contains delicate glauconitic mesh- 

 works of hexactinellid sponges and silicified portions of Inoceramus 

 and brachiopoda, besides an abundant series of heavy minerals : in 

 the Chloritic Chalk above the Glauconitic sponge-casts become 

 very abundant, associated with delicate casts of foraminifera ; the 

 White Limestone itself has scarcely any residue. The analyses 

 show that the percentage of carbonate of lime increases steadily from 

 base to summit, the Glauconitic Marls alone being an exceptiou. 



III. This section deals with the stratigraphical conclusions. The 

 Glauconitic Sands, regarded by Tate as equivalent to the lower 

 portion of the Upper Greensand, and by Barrois as synchronous 

 with the upper beds (Pecten asper-zons) of the same formation, are 

 regarded as having commenced to be deposited in the earlier portion 

 of that period, and to have been still forming during the Pecten 

 asjjer times in England. The Yellow Sandstones with chert are 

 mainly equivalent to the Warminster Sandstones with chert in the 

 S.W. of England. The above two beds therefore constitute the Upper 

 Greensaudin Ireland. The Escogyra-columba and Inoceramus- 

 Crispi? zones were both considered by Tate as Cenomanian, and 

 by Barrois as Turonian. In the present paper they are considered 

 as absolutely distinct, the Eocogyra columba-zone being truly Ceno- 

 manian (as limited by Jukes-Brown and Hill) ; the Inoceramus 

 Crispi?-zoiie, on the contrary, being similar in its fauna to the 

 Chalk Bock and lowest Senonian beds in England, and on theoretical 

 and faunal grounds being in preference assigned to the latter. 



The 3Iicraster-zones of the Senonian have been directly recognized, 

 but the higher ones of BelemniteUa vera (Marsupites) and B. qua- 

 drata are well represented. The nodular beds at the base of the 



