114 THE LIAS AMMONITES. 



THE UPPER LIAS. 



I include in the Upper Lias all the argillaceous, shaley, laminated, marly, and 

 arenaceous deposits interposed between the Spinatus-heds of the Middle Lias, and the 

 basement-beds of the Inferior Oolite, containing Harpoceras MurchisoncE. This group 

 of strata nearly corresponds to the " Posidonienschiefer mit StinJcsteinen" and " Licldgraue 

 Kalhnergel mit Ammoiiites jurensis " of Professor Quenstedt,^ and the " Neuvieme Etage ; 

 Toarcien " of the late Professor Alcide d'Orbigny.^ 



The Upper Lias exhibits great differences in thickness as we follow the beds north- 

 wards through the midland districts of England, in some parts of which it measures 300 

 feet, but rapidly diminishes in North Oxfordshire to 30, and disappears entirely in the 

 south of that county. In South Lincolnshire it attains 200 feet, and thins away entirely 

 in South Yorkshire, whilst in North-East Yorkshire it thickens out again, and forms 

 some fine bold instructive sections on the Yorkshire coast. 



The Petrology of this group, which in some parts of Gloucestershire is upwards of 

 300 feet in thickness, enables us to subdivide it into a lower portion, consisting of 

 dark argillaceous, shaley, or thinly laminated beds, and an upper portion composed of 

 marly, ferruginous strata, or fine yellowish and brownish sands. 



By a careful study of the Palaeontology of the Upper Lias I have been able to 

 distinguish among the numerous organisms contained therein four faunas, having several 

 well-defined species characteristic of each. The details of each of these zones will be 

 given in the sequel. 



It is very difficult to find a section in which all the zones are present and exposed 

 in their natural sequence, so I select that of Frocester Hill, near Stonehouse, between 

 Gloucester and Bristol, on the Midland Railway, as the best I know. 



All the divisions of the Upper Lias are here seen in situ, and may be satisfactorily 

 studied in one day's work; and this instructive section maybe afterwards advantageously 

 compared with other exposures of the Liassic sands forming the Jurense-zone at Hares- 

 field Beacon, a mile and a half from the railway-station, and at an elevation of 700 feet 

 above the sea; in lane cuttings near Nailsworth ; in sections at Uley Bury ; Stinchcombe 

 Hill ; Wotton-under-Edge; and along Ozleworth Bottom; all localities of easy access, in 

 which are well displayed the Liassic sands, and at the same time affording magnificent 

 pictures of the vale scenery of Gloucestershire. 



* ' Flotzgebirge Wiirtembergs,' pp. 213 and 267, 1843. 



- 'Cours Element, de Paleontologie et de Geologic stratigrapliiques,' torn, ii, p. 463, 1852. 



