1864.] TATE CRETACEOTTS ROCKS OF IRELAND. 17 



Bryce*, in 1852, more cautiously states that "indications of a 

 rudimentary development of some Oolitic strata have indeed been 

 noticed near Larne ; but as they have not been clearly made out, we 

 may pass them over here." 



Again, McAdamf, in 1852, observed that " at Larne a bed oi oolitic 

 structure rests upon Lias, and in it are found Avicida contorta, Lima 

 prohoscidea" «fec. ; while Professor King J (1863) similarly particu- 

 larizes the position of the quasi Oolitic formation, introducing in his 

 table oolitic beds probably of the age of the Bath Oolite, and said to 

 contain obscure impressions of Cardium, &c., as occurring near Larne, 



The beds which have been regarded as of Oolitic age by the above 

 writers, excepting, perhaps. Professor King, are to be seen in a fine 

 cliff-section on the coast south of Waterloo, Larne. They consist of 

 two beds, each about 5 feet in thickness, overlying indurated marls, 

 containing Avicida contorta, Cardiimi liliceticum, tfec. The lower bed 

 is simply an indurated marl with disseminated calcareous grains, 

 and presents an oolitic structure. The upper bed is made up of 

 spheroids of marl of the size of large peas. The marls that are asso- 

 ciated with these pseudo-oolitic beds belong to the Ehastic series, 

 and are surmounted by true Lower Lias, containing Gryphoia in- 

 curva, Lima tiibercidata, Terquem (L. prohoscidea), &c. I have also 

 seen similar beds of the same age at Cave Hill, Belfast §. 



The ' Larne mixed fossil-bed ' of Professor King is without doubt 

 that of BaUycraigy, near Larne, a specimen of which, in the museum 

 of the Natural History Society of Belfast, is labelled " Oolite, BaUy- 

 craigy." This specimen at first appears to be an oolitic limestone ; 

 but on a careful examination it proves to be only a fine-grained 

 siliceous rock, with a light-coloured calcareous cement. The block 

 bears an impression of the flat valve of Pecten quinquecostatus, and 

 . was evidently obtained from a bed which occurs above the basement- 

 bed of the Upper Greensand, and is a part of the upper series of 

 that formation. It is in fact the ordinary rock of that member 

 (which is a siliceo-chloritic rock with a calcareous paste), wanting 

 in the disseminated chloritic ingredient. The presence of P. quinque- 

 costatus is sufficient to prove its age without other evidence. There- 

 fore, with Professor Jukes || (1862), I contend that " the only beds 

 belonging to the Oolitic (Jurassic would have been more strictly 

 correct) series in Ireland are some black Liassic shales." 



2. Loiver Greensand and Gaidt. — The majority of the writers on 

 the age of the Irish Cretaceous beds have referred them to Upper 

 Chalk, Lower Chalk, and Upper Greensand, altogether or in part ; 

 yet a few have departed from such determinations. 



Bryce^I (1837) is one of the few authors who has regarded some 

 portion of the Cretaceous series as a probable equivalent of the Lower 



* Geol. Notices, Environs of Belfast, p. 10. 

 t Rep. Brit. Assoc, Trans, of Sect. p. 64. 



I Synoptical Table of British Aqueous Eocks, 5th edit. 

 § Quart. Journ. Geol. Soc. vol. xx. p. 108. 



II Manual of Geology, p. 589. 



^ Trans, Geol. Soc. 2nct ser. vol. v. pt. 1. p. 79. 

 VOL. XXI. PART I. C 



