130 ROMER’S DESCRIPTION OF THE CHALK 
IV. Upper Greensanp :—Firestone, Merstham beds. [Der 
Griinsand.—Glauconie crayeuse, craie chloritée.| 
This, according to Mantell, is in Sussex a sandy, argillaceous, 
grayish-green coloured deposit, consisting of marl and of gra- 
nules of silicate of iron, which sometimes form loose, sometimes 
compact masses. It generally passes very gradually into the gray 
chalk (plener) ; and varies in thickness from a few feet to 80. 
This formation is replaced in some districts by a bluish-gray 
compact chalk marl, which rarely alternates with green layers, 
and is called “ malm.” 
At Folkstone this formation occurs as a soft gray sandy marl, 
which is traversed in all directions by stem-like cylindrical green- 
spotted bodies, and contains numerous granules of silicate of 
iron; its thickness here does not amount to more than 25 to 30 
feet. At Godstone in Surrey, a deposit 4 inches in thickness of 
bluish-gray siliceous concretions (flints, chert) alternates with 
the green layers. 
A similar description has been given of this formation in 
France. 
In the North of Germany we meet very frequently with the 
flammen mergel (streaked marl), which appears to agree with 
the malm rock. The lower beds of the gray chalk-mar] (plener) 
sometimes gradually acquire a larger amount of clay, sand, iron 
and carbonaceous matter, and thus pass, or are suddenly changed, 
into a coarse earthy bluish-gray or yellowish-white marl, which 
is usually traversed by darker veins, streaks and spots, frequently 
exhibiting a thin slaty texture, and often alternating with harder 
and more siliceous seams, a few inches only in thickness. Not 
unfrequently, as at Simmenstedt, we find on this rock cylindri- 
cal, concentrically-wrinkled (concentrisch runzelige) concretions 
minutely spotted with green, about an inch in thickness, similar 
to those which occur at Folkstone; they frequently traverse the 
layers perpendicularly. This formation occurs thus beneath the 
plener at almost all the places where we have pointed out the 
latter. Its thickness is frequently considerable, and sometimes, 
as for instance at Wrisbergholzen close to Alfeld, amounts even 
to 400 feet, though in general much less. 
As regards the organic contents, Avicula grypheoides (Sow. 
Geol. Trans. 2nd Series, iv. plate xi. fig. 3) appears to be espe- 
cially characteristic ; with this occur Pecten laminosus, Belemnites 
