- 78 - 



which are not found at Horstead ; but with few exceptions 

 in this single Horstead flint, there are present all 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 h-eland 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 vai^iety 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 



