54 
On Denelioles. 
can hardly have been so abnormally perverse as to prefer— 
if wanting flint or chalk—to concentrate their excavations 
just where they got the least return for their labour. My 
maps (Plate I.) are taken from that of the Geological Survey 
showing the environs of London, and their object is simply 
to show the surface occupied by bare chalk as compared with 
that covered by the overlying beds. I have accordingly 
omitted all the subdivisions of the latter, the alluvial flats 
being alone separated on account of their value in illustrating 
the Physical Geography of these districts. 
On Plate II. of Mr. Spurrell’s paper are figured nine 
varieties of Denelioles, and it seems to me that Nos. 2, 3, 
and 4, which are all pits at Stankey, may be compared on 
terms of equality with the three we have already descended 
in Hangman’s Wood. The three simple forms, Nos. 7, 8, 
and 9, are all shallow pits in the chalk only. So far, indeed, 
we have seen no pillars in the pits at Grays, while each of 
the Stankey pits figured has one or more. But this marks 
simply a later stage of development in the Stankey pits, not 
a different plan of excavation. No. 1 Pit, Hangman’s Wood 
(Plate II.), may indeed have had at one time a general 
resemblance to No. 8 Stankey, and may owe the downfall of 
Thanet sand, which occupies so much of its space, partly to 
the thinness of its chalk roof (from one foot six inches to 
two feet) and partly to the removal of a pillar such as that 
still existing in No. 3 Stankey. But Nos. 2 and 3, Hangman’s 
Wood, have evidently not reached the pillar stage. The 
greatest length in each pit is seventy feet, and is along a line 
passing through the centre of the shaft and of the openings 
opposite each other at its base, by means of which admission 
is given to the cavern. In No. 2, on one side of the shaft, 
are two chambers with a direction at right angles to the line 
of greatest length. On the opposite side of the shaft, how¬ 
ever, there is a chamber on one side only, the sixth being 
entirely wanting. In No. 3 the sixth chamber is added, and 
the symmetry is complete. It would seem that there had 
been more demand for space in No. 3 Pit than in No. 2. 
For in No, 2 the chambers are very much narrower than in 
