412 A. EARLAND ON FORAMINIFERA. 



different at various levels in the same deposit. Some years ago 

 I brought a lot of material from the Gault of Folkestone, but 

 not being a geologist I was obliged to take the specimens at 

 random, and they did not prove very good. Since then, however, 

 Mr. Chapman has published his valuable papers on the Gault 

 Foraminifera in the " Transactions " of the R.M.S., and it should be 

 comparatively easy for any one to procure good material there. 

 The London Clay is, as a rule, barren of foraminifera, but there 

 is a zone running under London which is sometimes exposed in 

 excavations, from which they can be obtained. 



Some of the hard clays and shales, and a few of the softer- 

 limestones which resist disintegration in every other way, can be 

 disintegrated by repeated boilings in a saturated solution of 

 common soda. I found this very effectual with some grey Miocene 

 marls from Malta, and have also used it for reducing Radiolarian 

 earths from Barbadoes. 



Very fine foraminifera can be obtained from Chalk. Except 

 for systematic study, the collector will do well to confine himself 

 to the Upper Chalk, where the flints will furnish him with 

 abundant material. This is to be obtained in two ways : Firstly, 

 from hollow flints, the cavities in which are generally filled with 

 a white powder, consisting principally of sponge debris and 

 spicules with amorphous carbonate of lime, but foraminifera 

 are more or less abundant. Sometimes the specimens are ex- 

 tremely large and perfect, and occasionally they are chalcedonised, 

 while retaining their perfect form. As a rule, however, when 

 the foraminifera are chalcedonised they are more or less corroded 

 and distorted in the process. 



In collecting the flints, those of a rounded form should be tried 

 first, as they are more frequently hollow than the others, and 

 with a little practice it is possible to judge by the weight whether 

 a flint is hollow or not. 



The second source of material is from the pockets or hollows 

 on the outside of the large nodular flints. The chalk in these 

 hollows, not having been subjected to the same pressure as the 

 surrounding beds, is softer, and the foraminifera are better 

 preserved. 



The material, from whichever source, should be carefully dried, 

 and the flint splinters removed as far as possible. It can then 

 be cleaned in the usual manner. 



