Lias ammonites of the British islands / Лиасовые аммониты Британских островов

Before describing the Ammonitidae of the Lias I purpose giving a short account of the several zones of life into which this great formation is divided, with the view of defining their statigraphical distribution in time and space. More ample details on the subject will be found in the various works cited in the synonyms prefixed to the description of the different zones.
English geologists divide this formation into Upper Lias, Marlstone, and Lower Lias, but these subdivisions require additions and modifications in order to place the liassic beds of the British Isles in strict correlation with those of France, Switzerland, and Germany. For on the Upper Lias clays, in certain localities, are superimposed extensive arenaceous deposits, which, previous to the publication of my memoir on the Upper Lias Sands,1 were grouped with the Inferior Oolite, and in the Lower Lias are included several beds of clays and marls which, with the Marlstone of English authors, form the .Middle Lias of Continental geologists. <...>