452 



ME. S. S. BTJCKMAN ON THE 



[Nov. 1903. 



Table V. — The Cotteswolds and Dorset. — Comparative Thicknesses of 

 Deposits laid down during similar Times in the two Areas. 



Hemerce. 



Cotteswolds: — 



approximate 



average. 



Dorset Coast: — 

 Chideock. 



Remarks. 





Feet. 



Feet. 



Yeovil Sands = strata of* 



Opalinijormis ] 







Moorei and DumortiericB 



and I 



2 



37 



hemerae. 



Acdensis. J 







Bridport Sands = strata of 

 opaliniformis-Moorei he- 

 rn erse and part Dumor- 



Moorei \ 

 and ^ 







tierice. 



6 



199 



Upper Lias Clay of Down 



Dumortierice. J 







Cliffs, Dorset Coast — 

 strata of Dumortieria 



Dispansi 1 







hemera (in part). 



to 



2 



a few inches. 



Strata of dispansi hemera 



Striatuli. J 







as sands in Somerset, 

 attain the thickness of j 



Variabilis ] 







perhaps 50 feet. 



to \ 



300 



a few inches. 



Strata of Struckmanni he- 



Faldferi. J 







mera as Midford Sands at 

 Bath, attain a thickness 

 of about 70 or more feet. 



Cotteswold Sands = strata 

 of variabilis and Lilli 

 hemerae. 



Upper Lias of Bredon= 

 strata of Moorei to fal- 

 dferi hemerae, and per- 









haps earlier. 



ammonites were overwhelmed by inundations of mud, and that, 

 therefore, the time taken to deposit the bed was small. 1 When, 

 however, this Cephalopod-Bed is analysed into some six divisions, 

 each with its particular fauna, and when the strata are found to 

 increase perhaps a hundredfold in thickness in other localities, it 

 is seen that the Cephalopod-Bed was a slow deposit, and that 

 the number of specimens in a thin band of rock is not due to 

 any swarming of individuals at the time, but to long- continued 

 accumulations of shells where there was a great paucity of 

 sediment. 



IV. COMPARISON WITH NoBMANDY. 



While the subject of the Toarcian deposits is being considered, it 

 may not be uninteresting to make a comparison with an exposure 

 in Normandy. There is a section at Tilly -sur-Seulles (near Caen) 

 which is very interesting, because it shows in a few feet a sequence 



1 ' Monograph of the Great Oolite Mollusca ' p. 3. (Pal. Soc. vol. iv, 1850.) 

 See also my 'Monogr. Inf.Ool. Ammon.' pt. ix, p. 446. (Pal. Soc. vol. xlviii, 1894.) 



