RHAXELLA-CH ERT IN EPPING FOREST GRAVELS. 
257 
little (if any) that can be labelled as from the Lower Greensand. 
Eocene rocks are represented by small sarsens, by siliceous 
sandstones containing flint-splinters, and by rounded flint 
pebbles derived from Lower Tertiary beds. A small decayed 
Belemnite (possibly from the Chalk), and some fragments of 
shells of Inoceramus (certainly from the Chalk), are practically 
the only derived fossils noted, other than the crinoids and 
sponge-spicules preserved in some of the chert fragments ; and 
of contemporaneous fossils, or of unquestioned human imple¬ 
ments, no trace has been found. The workmen state that 
neither bones nor shells have ever been seen by them in this 
gravel. 
The above assemblage of rock-fragments points to deriva¬ 
tion approximately from the north-west, but as this Monk 
Wood Gravel is certainly Pre-Chalky Boulder Clay (which by 
no means implies Pre-Glacial) the agency by which these far- 
travelled rocks reached the gravel, in common with some high- 
level gravels of the Thames Valley (as, for instance, that at 
Dartford Heath, in Kent, where a very similar set of rock- 
constituents is met with), remains open to debate. 
No signs of contortions or “ trail ” have been observed in 
the Monk Wood gravel, and the overlying brick-earth rests with 
perfect conformity upon it, but, in September 1907, I found 
one waterworn piece of a crystalline felspathic rock which 
showed faint but certain striae and polish. 
One remarkable rock which occurred not infrequently in the 
Monk Wood gravel interested me greatly, both from its beauty 
when viewed with a pocket-lens, and also because one or two 
fragments contained casts of fossil shells. It occurred usually 
as angular or cuboidal pieces, the angles rounded, but otherwise 
little rolled, up to five inches by 3J inches by 3J inches, but 
sometimes as fully rounded pebbles. Fractured surfaces show 
an uniform buff colour, but v r eathered exterior faces may be 
bleached viiite, or stained deeper yelkwv by iron. When 
examined with a lens, a regular minutely vesicular structure 
is apparent, resembling delicate lacew’ork. 
Not until the present year (1913) w’as the identity of this 
interesting rock made known to me. Last spring I attended 
an excursion of the Geologists’ Association to Dartford Heath 
in North Kent, and there, in high-level gravel at 130 feet above 
