Reports and Proceedings — Geological Society of London. 333 



(c) The Eastern Division, extending along the Eastern coast from 

 the neighbourhood of Carrickfergiis to north of Carnlough, including 

 Island Magee. The Glauconitic Sands and Yellow Sandstones with 

 chert are present, but generally thinner than the same beds in the 

 Central area. In them dimyarian bivalves are very rare, Brachio- 

 pods of stunted forms, corals, and sea-urchins having been, on the 

 contrary, only found in them in this eastern region. The Exogyra 

 columba zone is barely represented, but the Inoceramns Crispi ? zone 

 (which Tate thought to be below that of Exogyra columba) attains a 

 thickness of over 20 feet, and evidence is brought forward to show 

 that it overlies the JSx. columba zone. There is a pal^ontological 

 unconformity between the two zones, the Irtoceramiis-beds passing 

 insensibly into the White Limestone without the intervention of a 

 conglomeratic bed. {d) The Peninsular Division. In the northern 

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

 on Arcbsean, 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 Rathlin 

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

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

 nata) 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 Upper Chalk times. 



(2) Chemical and Micromineralogical examination of the litho- 

 logical types. — The Glauconitic Sands are characterized by the 

 abundance of glauconite (23 per cent. CaCOj), showing evidence 

 of having been formed in the interior of foraminiferal shells ; the 

 Glauconitic 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 Inoceramus-zoiae contains delicate glauconitic mesh- 

 works of hexactinellid sponges and silicified portions of Inoceramus 

 and Brachiopods, 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 exception. 



(3) 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 Barrels as synchronous 

 with the upper beds [Pecten asper zone) 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 

 asper times in England. The Yellow Sandstones with chert are mainly 

 equivalent to the Warminster Sandstones with chert in the south-west 



