303 



PEOCEEDIKGS OF THE GEOLOGICAL SGCIEIY. [May 22, 



Formations. 

 Upper Lias. 

 Middle Lias. 



Lower Lias. 



Groups. 



Belemnite- 

 beds. 



Arielian. 

 Hettangian. 



Avicula- 

 contor 



i cilia- r 



ta Series. [ 



Zones. 



{A. raricosfatus. 

 A. oxynotus. 

 A. ohtusus. 

 \^A. Turneri. 



\ A. BucJdandi. 



J A. avgulatus. 

 \ A. 'planorhis. 

 f Whiie Lias {semu stricto). 

 \ Avicida contorta. 



In England tlie Hettangian series contains a well-deTeloped zone 

 oi Ammonites planorhis, whilst according to Dr. Wright* " the zone 

 of Ammonites angulatiis, so far as it has been exposed, appears to 

 be imperfectly developed in the British Isles ; and from the difficulty 

 experienced in separating its beds from the Bucklandi- series, they 

 were grouped with the latter in my memoir." 



This difficulty I have been enabled to overcome ; and the determi- 

 nation of the zone oi Ammonites angulatus with its characteristic fauna, 

 in the localities hereafter to be mentioned, rests on lithological, strati- 

 graphical, or palaeontological evidence, or on a combination of two 

 or all of these indices to the age of the horizon in question. 



II. OcCFREEiS^CES OE THE ZoNE OE AMMONITES AJS^GULATUS. 



1. h^eland. — The development of this zone in the neighbourhoods of 

 Larne, Belfast, Glenarm, and other places in the counties of Antrim 

 and Londonderry has been pointed out in my previous paper f. 

 The section at "Waterloo, Larne, I would employ as typical for 

 the rest of Great Britain ; for there the fauna is rich and charac- 

 teristic, the lithology is distinct, and the stratigraphical position 

 well-defined. 



The fossils from the north-east of Ireland are given in column 1 

 of the Table, pp. 311-313. 



2. Marton, near Gcdnshoroiigli, Lincolnshire. — The palseontological 

 evidence of the presence of this zone in the above locality, consists in 

 a large collection of fossils made by Messrs. F. M. Burton, F.G.S., 

 and H. Waugh, F.G.S., on the line of railway from Gainsborough to 

 Lincoln. No continuous section is exposed ; but the dull-blue earthy 

 and shelly limestones yielding the organic remains are known to 

 occupy a position intermediate between the marly clays and shales 

 with Ammonites planorhis and the blue compact limestones of the 

 " Bucklandi series ;" whilst lithologically and paloeontologically they 

 present the closest analogy to those of the zone of Ammonites an- 

 gulatus of several localities in Antrim. 



The fossils from this locality are given in column 2 of the Table. 



3. WanvicJcshire. — " This zone was well exposed in the Harbuiy 



* British Fossil Echinodermata, vol. 

 t Ante, p. 302. 



p. 63 (Pal. Soc. 1863). 



