548 L. F. Spath— 



On the Liassic Succession of Pabay, Inner Hebrides. 



By L. F. Spate, D.Sc, F.G.S. 



TT is intended to give in the present paper the results of the 

 -*- writer's collecting in the Lower Liassic (Carixian = Lower 

 Pliensbachian) Ammonite Beds of the Island of Pabay (Pabba), 

 known to fame since MacCulloch and Hugh Miller drew attention 

 to the abundance of its fossils and Murchison and A. Geikie collected 

 its ammonites. Some of these were many years ago described by 

 Sowerby and Wright, and in the more recent Survey Memoir ^ a list 

 of fourteen ammonite species was given, a number trebled in the 

 present account. Unfortunately, the hundred feet or so of micaceous, 

 metamorphic shale at Pabay is cut up by " dolerite and basalt 

 dykes and sills " to such an extent that the tracing of the succession 

 is not an easy matter. 



A comparison of the Pabay Lias with that of Dorset and other 

 areas will be attempted in a second paper. 



The reefs ofi the north-west coast of the island yielded numerous 

 examples of Uptonia jamesoni (Sow.) and Platypleuroceras hrevispina 

 (Sow.) and their allies, but the beds are extensively faulted and, 

 like the more barren south-east coast, did not offer a recognizable 

 sequence. On the other hand, the reefs between the two northern 

 extremities of the island, and those along the north-east coast, 

 where marked " Am. jamesoni " on the geological 1 in. map (sheet 71, 

 Glenelg), yielded a succession from the ibex, through the jamesoni, 

 down to the Sinemurian raricostatus zone. This may be represented 

 as follows : — 



Level Xg (Ledges east of faulted dyke at western of the two northern 

 extremities) : — 



Acanthopleuroceras maugenesti (d'Orbigny). 

 all. ,, ,, 



valdani (d'Orbigny). 

 an. ,, ,, 



inflatum (Quenstedt). 

 cf. carinatum (Quenstedt). 

 Liparoceras sp. ind. 

 Lytoceras fimhriatum (Sowerby) . 

 Ledges farther east, about three feet lower : — 



Acanthojjleuroceras aff. maugenesti (d'Orbigny). 

 Tropidoceras rotundum (Futterer). 

 Nine feet lower : — 



Tropidoceras sp. aff. rotundum (Futterer). 

 Ten to twelve feet lower : — • 



Tropidoceras masseanum (d'Orbigny). 

 Unfossiliferous ledges follow to the east, but twenty-five feet 

 lower were found : — 



^ " The Geology of Glenelg, Lochalsh, and South -East Part of Skye," 

 Sheet 71. Mem. Geol. Surv. Scotland, 1910, pp. 182-3. 



