240 ME. E. T. NEWTON ON MESOZOIC FOSSILS [^lay I9OI, 



In 1870 Prof. Tate ^ published a revised list of the Liassic fossils 

 of Ireland, and from this it will be seen that nearly all the 

 Rhastic and Liassic species found in Arran have been met with 

 likewise in the neighbourhood of Belfast. The Ehaetic fossils of 

 Arran indicate the former existence of strata corresponding with 

 the Avicula coi^or^a- shales, but at present there is nothing to 

 represent the White Lias in particular. 



That the Liassic fossils of Arran are from the earlier beds of that 

 formation is evident, and broadly speaking, they are equivalent to 

 the Lower Lias of the Belfast area ; but I think that we may take 

 another step with almost equal certainty. There seems no valid 

 reason for supposing that the Liassic specimens hitherto found in 

 Arran belong to more than one bed : for although some of the 

 specimens are very friable and others tolerably hard, this is due to 

 different degrees of decomposition. Now, among the fossils col- 

 lected are several examples of Ammonites anguJatus, while the 

 characteiistic ammonites of the Amm. planorhis- and Amm,. BucJc- 

 landi-zones have not been met with ; neither is there any fragment 

 of a belemiiite to indicate the ' Belemnite-shales.' It seems evident, 

 therefore, that our Arran specimens belong to the Ammonites 

 anr/ulatus-zone. Many of the species range into higher or lower 

 .zones, but all of them have been met with in Amm. anf/ulatus-heds 

 elsewhere. Quite possibly representatives of the other Liassic 

 zones of the Belfast area may yet be found in Arran ; but, as it is 

 the Ammonites angulatus-zone which attains the greatest thickness 

 around Belfast, so it may have been in Arran. The similarity of 

 the Chalk of Arran to that of Antrim lias already been remarked 

 upon. 



But for the preservation of tlie remnants above described the 

 presence of Mesozoic strata in Arran, other than the New Red 

 rocks, would have been unknown, and their preservation is due to 

 the accident of portions of the rocks having fallen into the neck of 

 a volcano. Being thus removed to some distance below the surface 

 of the country, they escaped the denuding influences that have 

 so effectually removed the other parts of the parent rocks which 

 there is every reason to believe formerly spread over the island of 

 Arran, and were doubtless continuous to the south-west with the 

 corresponding strata of the North-east of Ireland : forming also a 

 link between that district and the Liassic and Cretaceous areas of the 

 Western Islands of Scotland and the small Liassic district near 

 Carlisle. The still further extension of Cretaceous deposits in Scot- 

 land is indicated by the well-known remains of Greeusand age near 

 Moorseat (Aberdeenshire). 



The Liassic and Cretaceous rocks of the Western Isles of Scotland 

 are perhaps 100 miles north-west of Arran, and have been noticed 

 in part by the earlier writers mentioned in the more recent works 

 of Sir Archibald Geikie,^ Thomas Wright,^ and Prof. Judd^; but 



. 1 ' Irish Liassic Fcssils ' Eep. Belfast Nat. Field Club, j\pp. i (1870). 

 2 Quait. Journ. Geol. Soe. vol. xiv (1858) p. 1, ^ 3id. p. 24. 



^ Ibid. vol. xxxiv (1878) p. 696. 



