298 PROCEEBINGS OF THE GEOIOGICAl SOCIETY. [May 22, 



the Lias belongs to the Avicula-contorta series, which is invariably 

 the underlying stratum to the Lower Lias ; however, on the shores 

 of Lough Mourne and Larne Lough, and on the coast at Ballintoy 

 and Portrush, the base of the Lower Lias is not seen. And al- 

 though the shales of the Avicula-contorta series are usually covered 

 by the Lower Lias, yet, on the other hand, they are the last to dis- 

 appear in the thinning-out of the strata between the New Ked Sand- 

 stone and the White Limestone, which takes place beyond Garron 

 Point, on the north-east*. 



With regard to the Lower Lias, I have several emendations to 

 make — changes of slight importance when palaeontology is a secon- 

 dary consideration, but at the present of some value as exemplify- 

 ing the persistency of faunas over a large area, and elucidating the 

 nature of a zone. 



The Lower Lias in Ireland is capable of division into four mem- 

 bers ; the first, second, and third divisions I would correlate re- 

 spectively with the zones of Ammonites jplanorbis, Ammonites angu- 

 latiis, and Ammonites BucTclandi, the three lowest groups of the 

 Lower Lias in the Anglo-French and German basins. The fourth 

 zone represents the beds of the Lower Lias which are superior to 

 the zone of Ammonites Bucldandi. 



The first zone, that of Ammonites jplanorbis, is fairly developed, 

 but is questionably separable from the second, that of Ammo- 

 nites angidatits, which constitutes the greater mass of the Lower 

 Lias, and is most frequently the only portion present. The third 

 zone, that oi Ammonites Buchlandi", is (palaeontologically) easily to be 

 distinguished from the zone of Ammonites angidatus. The zone of 

 Belemnites acutus, the fourth of the series, represents the Belemnite- 

 beds of the Lower Lias of France, Germany, and England, and is 

 the highest member of the Irish Lias which I have seen ; it is litho- 

 logicaUy and palaeontologically well defined. 



2. Section at Waterloo, Larne. — This section is the key to the 

 reading of the Liassic strata in Ireland ; and I regret my inability to 

 place on record a more detailed representation of this fine cliff- 

 section than is here given. 



I may observe that at this locality the Avicula-contorta series is, 

 as a whole, a mass of indurated grey or brown marls, some few beds 

 of which are oolitic, and even pisolitic in structure f ; there is here 

 no line of demarcation between the beds with Avicula contorta and 

 the White Lias ; but this may be seen elsewhere in Antrim. The base 

 of this series is not seen ; but as the cliff, known by the name of Bank 

 Heads, 100 feet in height, is entirely composed of these beds, dipping 

 at an angle of 27°, their thickness cannot be less than 50 feet, and, 

 from other data, I compute the thickness of the Avicula-contorta 

 series at about 120 feet. 



Superior to certain grey marls are : — 



1. A succession of whitish marls and black shales ; these contain 



* The Avicula-contorta series reappears in the Tircreren Burn, on the north- 

 west, and a little beyond Colin Glen, near Belfast, on the south-west of the 

 Liassic area. t Quart. Journ. Geol. Soc. vol. rxi. p. 17 (1865). 



