Reviews — Geology of the Isle of Wig Jit. 227 



The Lower Greensand is now divided as follows : — 



Carstone _ 1 = Folkestone Beds, 



band-rock Series J 



It is remarked that the Carstone passes up into the Gault, and 

 that the Sand-rock Series passes down into the Ferruginous Sands ; 

 while between the Carstone and Sand-rock Series the boundary is 

 somewhat sharply defined, with an appearance even of slight erosion 

 at times, though there is no evidence of an actual unconformity. 

 Considerable interest, however, attaches to this subject, for in other 

 places (as pointed out by Mr. Strahan) the Carstone passes up into 

 the Red Chalk, which partly represents the Gault; while in the 

 Kentish area the upper part of the Folkestone Beds (the zone of 

 Ammonites mammiUaris) is by some authorities placed rather with 

 the Gault than with the Lower Greensand. Hence it seems pro- 

 bable that the base of the Upper Cretaceous series may ultimately 

 have to be taken to include the Carstone. 



With regard to the Gault, wdiile the main mass belongs to the 

 upper division, it would seem that to some extent the lower division 

 is represented palreontologically ; some few species have been added 

 to the general list of fossils, but there is room for further detailed 

 work on the paleontology of this formation. The Upper Green- 

 sand has been separated into the Malm Rock and Chert Beds ; and 

 the Chalk has been subdivided into Chloritic Marl, Middle and 

 Lower Chalk with Melbourn Rock, Chalk Rock, and Chalk-with- 

 flints. The cliff-sections showing the Upper and Lower Cretaceous 

 rocks have been remeasured, and important additions have been 

 made to the illustrative sections. 



In the classification of the Tertiary strata, we find some changes in- 

 troduced. The name Headon Hill Sands is (provisionally) employed 

 in preference to Upper Bagshot Sands, because they probably 

 belong to a higher zone than the Upper Bagshot Series of the 

 London Basin. They are overlain by the Headon Beds, which 

 form the base of the Oligocene division (or Fluvio-marine Formation 

 of Forbes). For the uppermost portion of this division the name 

 Hamstead Beds is now adopted instead of the "Hempstead Series" 

 of Forbes, as the former is the mode of spelling used in the Isle of 

 Wight. Mr. Reid has proved that these beds extend over a much 

 larger area in the island, and have a greater thickness, than was 

 formerly supposed. Concerning controversial points, it is remarked 

 that " Forbes's correlation is followed in this Memoir, for though 

 there are some minor points on which Prof. Judd's criticisms are 

 no doubt just, yet with regard to the main difference the recent re- 

 examination of the island and mapping of the beds on the scale of 

 6 inches to the mile have not supported Prof. Judd's contention, 

 but rather shown that Forbes's correlation must still be accepted." 



Many additions and corrections have been made by Mr. Reid to 

 the accounts of the Tertiary strata and to the sections illustrating 

 them; and an account of the Flora of the Pipe-clay in the Lower 



