gS The Irish Naturalist. [ A.pril, 



II. —The Cretaceous Strata of County Antrim. By Dr. W. 



FkaSER Hume, F.G.S. (^Qitarterly /ainni, Geal. Soc. London, \o\. liii., 

 1897, pp. 540-606), 



Prof. Tate iu 1865, and Prof, Barrois, of Lille, eleven years later, 

 investigated in detail the Cretaceons series of the north of Ireland, 

 Since that time, we have learnt a great deal respecting the zones of the 

 Chalk ; and now Dr. Hume, after his elaborate microscopic and quanti- 

 tative studies of the English strata, has given us a similarl}- careful 

 account of his researches on their Irish relatives. 



The author divides the Cretaceous area of the County of Antrim into 

 five parts In the "southern " division, only the highest strata were de- 

 posited, against the Triassic clays, as the Chalk sea gradually deepened 

 and extended. The series mapped as " Upper Greensand " iu this district 

 is shown to be a shore-bed of far later date — in fact, of Senonian age. 



In the " central "' and " eastern " divisions, the latter including Island- 

 magee, a fairlj' complete series exists, from the Upper Greensand zones 

 to that of Belemnitella mvcronaia. In the central area, the beds were 

 nearer a shore-line than in the eastern ; in the latter, Turonian strata^ 

 lost elsewhere by an unconformit3% were fortunately laid down and pre- 

 served. 



In the fourth or '* peninsular " area, we have the strata that were 

 deposited against the peninsula or island of ancient rocks stretching 

 from the highlands of Londonderry to Cushendun and Torr Head. Here 

 ao-ain, we find no Cretaceous deposits until this old ridge sank in Upper 

 Senonian times. The zone of Actinocaviax quodralus is represented by 

 cont>-lomeratic beds, above which we have the White Limestone of 

 Murlough Bay and Slieve Gallion. The interesting conglomerates of 

 Senonian age are superbly seen at Miirlough Bay, as is shown in the 

 important photograph furnished to the author b}' Mr. Welch, which i» 

 reproduced in a full- page plate. The reproduction, however, leaves 

 something to be desired, especially when compared with the type of 

 illustration provided for geologists by the Royal Dublin Society or the 

 Royal Irish Academy in this country. 



Similar physical conditions naturally prevailed against the southern 

 side of the great peninsula •, and signs of them are " suggested in the 

 northern portion of the Kastern Division '' (p. 567). 



The fifth or *"' northern " division includes White Park Bay, and may- 

 repay further work, especially when the beds are traced back toward.s- 

 Dungiven. On the coast, the White Limestone reaches in this division 

 its maximum thickness of about 112 feet. 



Dr. Hrme then proceeds with a characteristic investigation of the 

 chemical and mineral nature of successive zones of the Irish Cretaceous- 

 series, with a view to determining the conditions under which the beds 

 were laid down. He finally (p. 598) correlates the Irish and English 

 strata as follows : — 



The Glauconitic Sands, and overhing Yellow Sandstones, represent 

 the Upper Greensand of England. 



