On Lower Lias Ammonites from Skye

Abstract

The writer has thought it desirable, in the following observations, to embody the results of his examination, last September, of the Arnioceras-bearing beds of Ardnish, near Broadford in Skye. The strata yielded a number of Ammonites of the Upper Coroniceras, gmuentdensis, and Ætomoceras subzones, and belong chiefly to the “Shaly Beds” of division iv of the Broadford Beds of the Survey Memoir on “The Geology of Glenelg, Lochalsh, and the South-East Part of Skye” (1910). They are therein referred, as by Professor Judd in his well-known paper on “The Secondary Rocks of Scotland”, to the bucklandi and semicostatus zones. Judd, the founder of the zone of A. semicostatus, certainly, however, misidentified some of his Ammonites, besides confusing his Lincolnshire A. geometricus with Young and Bird's A. semicostatus of a much higher horizon. Similarly, the Rev. J. E. Cross, in his paper on the “Geology of North-West Lincolnshire” (Q.J.G.S., vol. xxxi, 1875), recorded A. semicostatus from both the lower Gryphcæa incurva beds and the higher Scunthorpe Ironstone, which presents close analogy with the gmuendensis-Ætomoceras-Agassiceras beds of the Harzburg Ironstone. In reality this Ammonite (Arnioceras semicostatum) occurs in a much higher zone than either of these Lincolnshire beds.