462 Dr. Fitton's Additional Remarks. 



nected are strongly characterised and well defined — or those 

 derived from the names of places, where the beds are fully dis- 

 played and have been sufficiently examined: — as in the case 

 of the Portland limestone, the Purbeck beds, and the Hastings 

 sands. I am upon the whole disposed to prefer denominations 

 of the last mentioned description, since the very terms them- 

 selves point to the types in which the characters of the strata 

 are best exhibited ; and if the place which furnishes the name be 

 easy of access, geologists will find no difficulty in' recurring to 

 the standard, for the purpose of verification, in doubtful cases. 



From these combined considerations, I should propose to 

 distinguish all the strata which form the subject of my last 

 communication by different names; and, for the present, not to 

 group them together. And as the firestone beds are well dis- 

 played at Merstham, near Reigate, a place within a few hours' 

 journey from London, while the cliffs at Shanklin and its 

 vicinity, in the Isle of Wight, exhibit very distinctly almost every 

 form of what has been called greensand, — in a district which 

 must always be interesting to geologists, — I would suggest 

 the adoption of the following series of names, with the hope of 

 preventing ambiguity in future : — 



Proposed names of the Synonymcs. 



strata. 



1. Chalk Including chalk ivith and without fints — 



(the craie blanche of the French) and grey 

 chalk — chalk marl of Mr. Webster. 



2. Merstham beds . Firestone. — Greensand of Mr. Webster, Isle 



of Wight. — Tujfeau. — Craie-chloritee or 

 Glauconie-crai/euse of the French.* 



3. Gault Folksl one-marl. — Blue marl of Mr. Webster 



in the Isle of Wight. — Golt-brick-earth of 

 Smith's county maps. — Tetsworth-clay? 



4. Shanklin sands. Greensand — commonly so called. — Upper 



part of the ferruginous sands of Mr. 

 Webster. — Glauconie crayeuse f 



5. Weald clay .... (By some considered as the same with the 



clay of Tetsivorth, which, however, is 

 probably the gault ?) 



6. Hastings sands. Iron sands. — Lower part of the ferrugi- 



nous sands of Mr. Webster, I. of Wight. 



* The presence of chert is mentioned by Mr. Brongniart as characteristic of the 

 craie-tufau : but the relations of the Glauconie-crayeuse are rendered doubtful by 

 what the same author has mentioned of its separation in some cases from the Tufau 

 by a bed of bluish clay marl. (See Ann. des Mines, i. 254-5, 257-8, and vi. 550, 547 ; 

 or the translations in Mr. De la Beche's "Selections," &c. 1824.) 



