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 Palaeozoic 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- 



