450 



7^. M. Brydone — Zone of Offaster pihda 



Brought forioard 

 Strong marl seam, very yellow. 

 ^ /"Chalk with O. pilula of exceptional size 



. 





Flint seam . 

 Chalk with large 0. pihda 

 I Marl seam. 



V Chalk with 0._2JiZ«Za 



Marl seam. 



Cinct'us f Chalk without marl seams. No 0. jnhda 

 belt, t observed ....... 



Chalk with O.pilula, stretching 5 feet above 



and 10 feet below a parting. No marl 



^ ^ '^ 1^ seams or definite fiint seams 



V 



48 



15 



O 



84 



:j S 'si 



Chalk 

 Chalk 

 Chalk 



Strong flint seam. 

 Weak marl seam. 

 Strong marl seam. 



TJintacrinus 

 band. 



Indications of a marl seam. 

 ^Chalk with perhaps a slide plane at its base 



'Chalk, very confused and doubtful, perhaps 

 bounded both above and below by slide 

 planes ....... 



Chalk 



Flinty chalk, yielding Marsjqntes 



Chalk 



Flint tabular. 

 ^Chalk with Marsupites in lower part . 



Marl seam and parting. 

 -! Chalk with JJintacrinus at base . 



Marl seam and parting. 



293 6 



The subzone of abundant 0. pihda is easily recognizable here in its 

 broad features and capable of definite measurement. Closer search 

 than I had time to make would probably enable more of its minor 

 features to be supplied, seeing- how closely the lithological and 

 palseontological details at its top coincide with those noted in the 

 same position in Hants, Sussex, and the Isle of Wight. It might also 

 be possible to identify some of the characteristics of the subzone of 

 Echinocorys scidatus, var. depressus, although the section becomes 

 very unfavourable by the time this horizon is readied. I have 

 taken as the boundary between my zones of 0. pilula and Marsupites 

 the level at which, calculating from the lower boundary of his 

 Marsupites band, which can be identified with practical certainty, 

 Dr. Rowe found his highest plate of Marsupites. My own finds of 

 Marsupites did not carry it outside these limits. 



The thickness Dr. Rowe assigns by measurement to the combined 

 zones of 0. pilula and A. quadratus is 204 feet. My corresponding 

 measurement is 189 feet, a very near agreement under the 

 circumstances. 



