— 7 — 
which are not found at Horstead; but with few exceptions 
in this single Horstead flint, there are present a// the detached 
forms of spicules which have been found both at Haldon and 
in Ireland and Westphalia. Of the 34 different forms of 
spicules from the North of Ireland which were obtained 
from the contens of hollow flints from 36 different 
localities all the forms except one are met with in 
the single flint at Horstead. Detached sponge spicules 
are also known from the Upper Chalk in the South 
East of England but up to the present, so far as I am aware, 
no published description has been given of them. The few 
sponges described hitherto from the Upper Chalk of England 
belong to the Lithistidae and Hexactinellidae whose more or 
less complete skeletons occur in a few localities, but are by 
no means generally distributed. From these sparsely distri- 
buted specimens no one would be justified in stating that the 
sponges played an important part in the building up of the 
Upper Chalk of England. And even at Horstead one would 
be extremely fortunate to find a fragment of sponge skeleton 
in the Chalk itself. Yet in this same locality the contents 
of this hollow flint make it manifest that sponge life was equally 
as abundant and varied, and contributed as great a share to 
the deposits of the cretaceous ocean as these organisms do 
to the present deep-sea deposits in the Atlantic. The per- 
fect state of preservation, not only of the sponge spicules, but 
also of the tender shells of foramenifera and ostracoda which 
in marvellous variety of form are all mingled together in the 
cavity of this flint, proves that this flint meal contains a fair 
sample of the organisms which originally formed the creta- 
ceous ooze, if we except however the coccoliths which are not 
preserved. Subsequent metamorphism has altered this ooze, 
filled with perfect organic remains, into the present beds of 
Chalk and layers of flint nodules. As already noticed, the 
organic remains in the flint meal have not altogether escaped 
a certain degree of alteration, which has affected their mineral 
