1867.] TATE LOWER LIAS OF IRELAXD. 299 



no fossils, but the "beds serve to establish a lithological transition 

 from the Avicula-contorta series to the Lower Lias. 



2. Black indurated shales with flattened specimens of Ammonites 

 jplano rb i s, ixiid a few IToUusca, about -iO feet, in thickness. These 

 shales represent the zone of Ammonites lolanorUs. 



3. An alternation of shelly subcrystaUine limestones of a blacldsh 

 or greyish colour, from 1 to 2 feet in thickness, and blue marly clays 

 varying from 4 and 6 to 10 feet in thickness — the whole about 35 feet. 

 The limestones are very fossiliferous, and the faima is that which 

 characterizes the zone of Ammonites angulatus. 



4. Compact blue argillaceous limestones, weathering white, charged 

 with Gryphcea incurva, 



A few feet only of this zone is exposed beneath the raised sea- 

 beach near the Coast Guard Station. 



5. In the lluseum of the Philosophical and Xatural History Society 

 at Belfast, there are a few fossils imbedded in a micaceous clay, 

 obtained near ^^aterloo at low water. The fossils and clay are like 

 those of Ballintoy, where the beds, hereafter to be described, are 

 superior to those yielding Gnjiolicea incurva, and are referable to the 

 zone of Belemnites acutus. 



3. The Zone o/ Ammonites planorbis. — There are few sections which 

 exhibit the series embraced from the top of the Xew Bed ZvTarls to 

 the fossiliferous bedsjjro' excellence of the Lower Lias, as it is gene- 

 rally masked and disturbed by slips. But in every knowm expo- 

 sure, black shales with few fossils are interposed between the zone 

 o£ Ammonites angulatus and the Avicula-contorta shales and marls. 

 These black shales I refer to the zone of Ammonites planorbis, the 

 lithology of which, in other parts of Europe, as in Ireland, partakes 

 more of the nature of shale than of limestone. Its fauna is not cha- 

 racteristic, and it is only when contrasted with that of the overlying 

 zone that it is worthy of note ; it comprises a few species of the 

 Avicula-contorta %Qvie^, possibly a few peculiar forms, and some spe- 

 cies common to it and to the zone of Ammonites angulatus. If in the 

 Avicula-contorta zone we have a foreshadowing of Liassic ty^3es of 

 life, then the fauna of the Ammonites-jjlanorbis zone is the dawniog 

 of the rich series called Hettangian. 



The " Planorbis -beds " are readily recognized by their lithological 

 characters and by the paucity of species ; and I have determined 

 their presence in the following localities : — 



(1.) Colin Glen, five mile's south-west from Belfast. — The beds 

 Nos. 3 and 4 of this section *, which I had referred doubtfully to the 

 Lower Lias, I would now place as the representatives of the bed Xo. 2 

 of the AVaterloo sectionf ; they consist of shales and shelly limestone, 

 of an aggregate thickness of 21 feet 3 inches, which overlie White 

 Lias, and are subordinate to beds of the Ammonites-angulatus zone. 



(2.) Whitehead. — Similar shaly beds to those at Cohn Glen have 

 been observed by my valued friend J. Anderson, Esq., E.G.S., in the 

 imdercliff of this locality, whence he has obtained Ammonites pla- 

 norbis, Mytilus minutus, and Hemipedina. 



* Quart. Jourii. Geol. Soc. vol. xx. p. 109 (1864). t Vide supra. 



VOL. XXni. PAPvT I. Y 



