Jurassic Chronology: I Lias

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Abstract
I. Introduction. During the last few years 1 I have been engaged to examine a series of ammonites and brachiopods—some thousands of specimens—collected by the officers of the Geological Survey of Scotland in the islands of the Inner Hebrides off the west coast of Scotland—Mull, Skye, Raasay. As the thickness of these Oolite-Lias deposits is very considerable and specimens are in many places numerous, the faunal sequence is often observable to great advantage; and, as new faunal elements have been disclosed in some cases, the Oolite-Lias chronology requires a certain amount of elaboration and revision. By the kind permission of the Director of the Geological Survey I am allowed to give an abstract of certain results. These data, when compared with those which have been gradually accumulating about other districts, throw an interesting light on the faunal sequence in certain strata, and, though admitting that all suppositions are not yet proved, I venture to offer to the Society an epitome of evidence and surmise with the idea of drawing the attention of other workers to the particular points about which further investigation is desirable. The classical paper on the Scottish area is that by J. W. Judd. 1 He proposed the terms ‘Scalpa Sandstone’ and ‘Pabba Shales,’ and, though working under great difficulty, showed considerable acumen in his zonal classification: he recognized the presence of the zones of humphriesianum, murchisonae, spinatus, margaritatus, ibex, jamesoni, armatus, oxynotus, semicostatus , and bucklandi . A more elaborate faunal sequence is put forward at

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