Lower chalk—general account. ^ 
13 
lie termed Ghloritic Marl from an overlying “ Phosphatic Marl,” 
and in a much later paper* (1882) he calls the latter the “ Fossili- 
ferous Marl,” still applying the name Ghloritic Marl to the under¬ 
lying bed. Mr. Norman had, however, informed us in 1880 that 
both these beds were included by Captain Ibbetson under the 
name Ghloritic Marl, and as he had often accompanied Captain 
Ibbetson, his testimony is of value. 
There is, however, near Ventnor a third bed below the other 
two, and separated from what Mr. Norman calls the Chloritic Marl 
by a layer of rolled stones and phosphatic nodules. This is the bed 
referred to by Mr. C. J. A. Meyer in 1878, who regarded it as 
part of what had been called Chloritic Marl, and maintained that 
under this name there were included two beds, “ which, although in 
actual contact, were in age widely separated,” the one being the 
(local) top of the Upper Greensand and the other the (local) bottom 
of the Chalk Marl. This is quite true of the beds referred to by Mr. 
Meyer, but we do not think that the lowest bed was ever included 
by Captain Ibbetson in his Chloritic Marl. 
Meantime the name Chloritic Marl had been applied to beds at 
the base of the Chalk in Dorset, Hants, and other counties. Mr. 
H. W. Bristow was surveying the western part of Dorset during 
the years 1846 and 1847, and the Geological Survey map (Sheet 18) 
was published in 1850. No descriptive memoir of it was issued, 
nor was any paper on the Chalk or Greensand of West Dorset pub¬ 
lished either lay Mr. Bristow or by Professor Forbes, who examined 
the fossils collected from the district; but it is known that they 
regarded the basement bed of the Chalk in Dorset as the equivalent 
of the Chloritic Marl of the Isle of Wight. Thus Professor Forbes, 
under the description of Galerites castanea, f mentions the “ Chlori¬ 
tic Marl ” of Dorset, and the abundance of that fossil in it; and 
Mr. Bristow has recorded the opinion of Professor Forbes]; that the 
“ Chloritic Marl ” of Dorset belonged to the Chalk and not to the 
Greensand, because Scaphites cequalis is a common fossil in it. This 
is true of the Dorset bed, but not of that in the Isle of Wight, and the 
facts as at present known make it probable that the nodule bed at the 
base of the Dorset Chalk is not the exact chronological equivalent of 
any part of the Chloritic Marl of the Isle of Wight, but is of slightly 
later date. 
Again, Mr. Meyer had come to the conclusion in 1874 that certain 
beds at the base of the Chalk in Devonshire represented the Chlori¬ 
tic Marl of the Isle of Wight; and as many of the fossils occurred 
also in the highest bed of the Upper Greensand near Warminster 
(Rye Hill Sand), he thought that this also should be called Chloritic 
* Geol. Mag., Dec. ii. Vol. ix. p. 440. 
t Decades of the Geological Survey, No. III., 1850. 
X Geology of the Isle of Wight. Mem. Geol. Survey. Second edition 
( 1889 ), p. 80 . (Not in the first edition.) 
