Vol. 67.] WEST, MID, AND EAST SOMERSET. 7 



Thus, while the Westbmy Beds above Bed 15 can be correlated, 

 as regards their component deposits, very tolerably, the same 

 remark does not apply to those below that bed. 



The black shales of the Westbury Beds in this country usually 

 give place somewhat suddenly to pale marls and equally pale 

 associated limestones. The difference in lithic structure between 

 the Westbury Beds and these succeeding ' Gotham Beds,' as they 

 may be called, is nothing as compared with the difference in 

 faunas. These dissimilarities suggest interruption in sequential 

 deposition, and the probability of such interruption is seen when 

 the beds near the junction-line of the two subdivisions are studied. 

 In the railway-cuttings at Sparkford Hill and Charlton Mackrell 

 the great boulder-like masses of stone at the top of the Black Shales 

 point in the same direction as does the interesting discontinuity 

 of the pale greenish-grey deposit at the base of the Cotham Beds 

 at St. Audrie's Slip, near Watchet. The causes producing these 

 phenomena effected the initiation of conditions suitable for the 

 formation of the pale deposits which — as already remarked — may 

 be called the ' Cotham Beds/ with their interesting assemblage 

 comprising Estherice, ostracoda, and Lycopodites. 1 



Upper Rhsetic. 



Cotham Beds. — The succeeding division of the Rhsetic Series, 

 the • Upper Rhsetic ' of my former papers, or the ' Cotham Beds,' 2 

 differs (as already hinted) considerably from the one which 

 it overlies. The component deposits are very different, and so 

 too is the fauna. Pale marls and limestones largely compose it, 

 and at certain horizons ostracoda, plant-remains, and Estherice are 

 abundant. The bed in which the Estherice and plant-remains 

 mainly occur in Worcestershire and North- West Gloucestershire is 

 a well-marked limestone with arborescent markings, and, except 

 for the Pseudomonotis Bed or its equivalent, is the only limestone 

 in the Cotham Beds. But, from the neighbourhood of Chipping 

 Sodbury southwards to that of Bristol, there are usually a number 

 of impure argillaceous limestone-bands in the Cotham Beds, and 

 phyllopods, as also remains of lycopods, occur at several horizons ; 

 while over the greater part of Somerset there are at least two 

 noticeable limestone-bands, in addition to the Cotham Marble or its 

 equivalent. Ostracods are most abundant immediately below the 

 Estheria Bed, but occur also in the marls above. The Cotham 

 Marble is frequently rich in specimens of Pseudomonotis fallax ; and, 

 of course, in the Pseudomonotis Bed of Garden Cliff such specimens 



1 Lycopodites and Estherice have not been discovered, so far as I am aware, 

 south of the Mendip Hills. Hapsford Mills in Vallis Vale is the southern- 

 most place at which I have obtained them. 



2 After Cotham, near Bristol, where the Cotham Marble is well-developed. 



