12 THE LIAS AMMONITES. 



The Lower Black Shales rest upon beds of pale green and grey marls, interstratified 

 with bands of limestone which are here interposed between the Contorta-series and the 

 Red Marls of the Keuper. 



In this cutting, when first made, the uppermost portion of the grey marls was overlain 

 by a thin bed of conglomerate formed of small round quartz pebbles, and on this rested 

 the basement layer of the Black Shales. The Bone-bed was uniformly thin and found with 

 difficulty in situ, although fragments of it were* discovered on the spoil-banks. I have 

 collected from these many good specimens of teeth and scales of the Fishes in the list. 



The Lower Pecten-bed is a slate-coloured, pyritic, semi-indurated shale, containing 

 many compressed bivalved shells in tolerable preservation, and the dark shales between 

 the two Pecten-beds have a few fossils closely compressed between the laminae. 



The Upper Pecten-bed was very rich in Conchifera, which were enclosed in a hard, 

 argillaceous limestone with iron ; so the fossils were too pyritic to be preserved, other- 

 wise a larger list might have been added. 



At Puriton is another railway-cutting in which the Contorta-series is well exposed ; 

 and the Bone-bed was found to be richly fossiliferous. In this cutting the Ostrea- and 

 Planorbis-beds of the Lower Lias were likewise well laid open. 



The railway-cutting near Shepton Mallet affords another instructive section of the 

 Contorta-series overlain by the Ostrea-, and Planorbis-, and Angulatum-beds of the Lower 

 Lias ; and similar sections are exposed likewise near Wells, and Whitchurch, and at 

 Saltford and Weston, near Bath. The latter show the relation of the Contorta-series to 

 the Lias extremely well, as will be seen in the sequel. 



A very fine coast-section of the Contorta-series, ranging from the tea-green and grey 

 Marls through the Black Shales and Limestones of the Lower Lias, is admirably 

 exposed at St. Audrey's Slip, two miles east of Watchet. At the base are seen the red 

 marls of the Keuper having in succession the tea-green marls, and above alternating beds 

 of pale-grey, hard, and soft marls, resting on beds with strontian and gypsum. The pale 

 grey marls are overlain by black shales, which collectively are here about forty feet thick, 

 and almost unfossiliferous. The black shales are overlain by a band of nodular lime- 

 stone containing Cardium Rhaticum, Axinus depressus ; above this band comes in dark 

 grey, sandy shales with the Bone-bed, consisting of a grey calcareo-siliceous rock, enclosing 

 the teeth of Saurichthys apicalis, Acrodus minimus^ and Hybodus. The Bone-bed is overlain 

 by dark shales, and inconstant bands of limestone, containing Avicula contorta, Pecten 

 Valoniensis, Anatina Suessii, Myophoria posfera, and other Conchifera. The dark-grey 

 shales, some of which are indurated and ripple-marked, are sixteen feet thick, and are 

 overlain by the Cotham Marble-bed, on which rests eight feet of the White Lias series, 

 containing the Sun-bed ; on this reposes a series of laminated shales five feet thick, some 

 of the beds containing immense numbers of Pullastra, similar to the condition of the same 

 beds at Pinhay Bay, on the Dorset coast. These shales separate the White Lias from 

 the Ostrea-series, fifteen feet thick, which succeeds in the section. 



