PREFACE. 
In the following pages I have attempted to give 
a description of the forms and affinities of a number 
of sponge spicules which were present, with a number 
of other organic remains, detached and heterogenously 
mingled together, in the cavity of a single flint stone, 
from strata of the Upper Chalk Formation, at Hor- 
stead, a village but a few miles distant from the city 
of Norwich, England. 
The way in which I met with the material which 
yielded these sponge spicules is as follows: Returning 
to my native city after an absence of several years 
during which I had studied the Paleozoic rocks of 
North America, my interest was naturally excited by 
the contrast between the chalk and the limestones of 
the older rocks, with which I had become familiar, and 
I determined to examine the numerous pits, as they 
are termed, in which sections of the chalk were ex- 
posed to view, in order to become farther acquainted 
with the strata and to collect fossils for future study. 
With this purpose I went one. day to a pit at 
Horstead, but found on my arrival that some long time 
had elapsed since the chalk had been worked; for al- 
ready the section was partly obscured by a talus of 
gravel which had fallen from the overlying beds of 
rolled and stratified flints, and by the crumbling of 
the chalk itself, so that the prospect of obtaining fos- 
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