80 GEOLOGY OF THE ISLE OF WIGHT. » 



freestone as the zone of Pecten asper, which fossil is recorded 

 from the freestone. Mr. Parkinson, however, denies that Pecten 

 asper occurs in the Isle of Wight at any other horizon than in 

 the Chloritic Marl, and that there it only appears as a derived 

 form,* in a layer of broken specimens at the base of the upper- 

 most l)ed of this subdivision near Ventnor. This Pecten being 

 a characteristic Upper Greensand form, its occurrence as a 

 derwed fossil only in the Chloritic Marl seems to indicate that 

 this bed is in part made up of the reassorted materials of the 

 Upper Greensand. All the phosphatised fossils which occur in 

 the Chloritic Marl are also of Upper Cretaceous type, and, 

 though they appear to have been phosphatised in a matrix similar 

 to that in which they are now imbedded, namely a glaucouitic 

 sand, they have all been broken and many have been rolled. 



Near Ventnor and St. Lawrence the Chloritic Marl is divisible 

 into two or more bands, the uppermost of which contains the 

 numenius pbosi)hatic casts before alluded to.t According to 

 Mr. Meyer,J there are included under this title of Chloritic Marl, 

 as first applied, *' two sets of strata with, in time at leaet, a gap 

 between them," the (local) top of the Upper Greensand, and the 

 (local) bottom of the Chalk Marl, the lower including in its fauna 

 Pecten aspe?-, Tcrehratella pectita, Gatopijgus carinatns {colum- 

 barius), Echinoconus [Galeritei) castanea, &c., the upper. Ammo- 

 nites, Scaphites, Turrilites, Sfc, mostly phosphatic. These two 

 sets he correlated with the beds overlying the Chert Beds at 

 Warminster, for which he had previously used the name of the 

 Warminster Beds. 



But Mr. Jukes-Browne§ remarks that the Warminster fossils 

 occur only in a remani4 form in the Chloritic Marl of the Isle 

 of Wi»ht, and that the small indigenous fauna differs very little 

 from that of the Chalk Marl, but is quite distinct from that of the 

 zone of Pecten asper. The Chloritic Marl is therefore regarded 

 by him as the natural base of the Chalk. 



Not only, however, is it impossible to recognise sub-divisions in 

 the Chloritic Marl throughout the Island, but it is almost as 

 difficult to fix on a definite line between it and the Chert Beds. 

 While palseontologically it forms the base of the Chalk,|| litho- 

 locicaliy it is Upper Greensand, aad the only line which can be 

 traced across country is that which runs at the foot of the Chalk 

 Downs, and marks the position of the lowest bed of chalk. Over a 



* Quart. Journ. Geol. Soc, vol. xxxvii. p. 372. 188L 



f This upper band seems to have constituted the Chloritic Marl of Captain 

 Ibbetson, M-ho gives a thickness of 1 to 3 feet only to the bed. " Notes en the 

 Geolog3', &c. in the Isle of Wight," p. 24 (but see also p. 2] where he speaks of it 

 as consisting of two portions, the upper exhibiting a conglomerate of pebbles and 

 sma'il boulders). 



X Gcol. Mag. for 1878, pp. 547-55 L See also Quart. Journ. Geol. See, vol. xxx. 

 p. 369. 1874. 



§ Geo/. Mag. for 1877, p. 357. 



il When the geological mapping of Dorset was undertaken by H. W. Bristow, E. 

 Forbes, the palaeontologist, pronounced that the Chloritic Marl, containing Scaphites 

 aquali's, constituted the lowest bed of the Chalk, of the fossils of which this formed 

 the earliest appearance. — H. W. B. 



