384 HISTORY OF GEOLOGY AND PALAEONTOLOGY. 



tion of the Foraminifera^ completely overthrew the older 

 classifications and formed the basis of our present intimate 

 knowledge of these exquisite little shells. 



Carpenter divided the Reticularia into two sub-classes : 

 Imperforata and Perforata, and sub-divided each of these sub- 

 classes into several families distinguished according to the 

 chemical composition and microscopic structure of the tests. 

 The views held by Carpenter and his collaborators, Parker and 

 Jones, regarding the confines of the genera and species, 

 differed very considerably from those of D'Orbigny, as the 

 English zoologists often comprised under the same generic 

 title forms very different in their external appearance, on the 

 plea that they were connected by intermediate types. 



Reuss has published from 1839 onwards a large number 

 of papers, mostly in the Transactions of the Vienna Academy, 

 describing individual species of fossil Foraminifera from 

 all geological formations. The works of Parker and Jones, 

 extending from the year 1857, follow the same direction 

 of special research. The classifications of Schwager and 

 Brady introduced several modifications of Carpenter's scheme. 

 Brady pointed out that the sub-classes Imperforata and Per- 

 forata could not be so sharply defined as had been done by 

 Carpenter, for example the group Lituolidea, which Carpenter 

 had ranked under the sub-class Imperforata, included also 

 certain species which were finely perforate. This matter, 

 along with other systematic difficulties, has been more recently 

 discussed by Ray Lankester, in his descriptive and classifi- 

 catory account of the Protozoa, published in the Encyclopaedia 

 Britannica. Brady's Report on the Foraminifera of the Chal- 

 lenger Expedition, and his monograph of the Foraminifera in 

 the Carboniferous Limestones of Great Britain, are two of the 

 finest productions in this domain of research. 



In the French literature of the Foraminifera, the excellent 

 monograph of the Nummulites by D'Archiac and Haime takes 

 the highest place. Terquem and Berthelin even at the present 

 time are wholly disciples of D'Orbigny. Meunier-Chalmas 

 and Schlumberger have, on the other hand, placed great 

 significance on microscopic researches of the shell-architecture, 

 and have made many interesting observations on dimorphic 

 forms of the initial chamber. In Italy, Michelotti, Seguenza, 

 Silvestri, and more particularly Fornasini, have described the 

 Foraminifera present in the younger Tertiary deposits. 



