10 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 77 



GEOLOGIC DISTRIBUTION 



Foraminifera are known from most of the sedimentary rocks. They 

 occur very abundantly in the Cretaceous and Tertiary of all parts 

 of the world. In the Palaeozoic they seem to be more restricted in 

 their distribution. In the Carboniferous, for example, Fnsulina forms 

 thick limestones, and various species occur in less abundance in other 

 Palaeozoic formations. Certain groups of foraminifera become abun- 

 dant and characteristic in certain geologic formations. Fnsulina and 

 allied forms are very characteristic of certain parts of the Carbon- 

 iferous. In the Cretaceous the Textulariidae and many Miliolidae 

 become very abundant. The latter probably reaches its highest devel- 

 opment in the upper Cretaceous, In the early Tertiary the Num- 

 mulitidae become dominant, and form very thick limestones in the 

 Eocene and Oligocene. 



It is through the knowledge of the distribution of the various species 

 and genera in various geologic formations that the great economic 

 use of the foraminifera lies. When type sections are known in detail 

 it becomes possible by the study of well cuttings to determine sub- 

 surface structure. As a result much is being done in the way of the 

 refinement of the study of fossil forms, and the limits of range of 

 many fossil species. When this work is done thoroughly it makes the 

 foraminifera one of the greatest assets to the geologist in economic 

 work. 



METHODS OF HANDLING 



RECENT MATERIAL 



Collecting. — For systematic work, especially in deep water, it is 

 necessary to have elaborate and rather expensive apparatus. For this 

 reason most of the work in deep waters has to be carried on by 

 governmental vessels, or by especially equipped expeditions for the 

 purpose. Such work was first attempted on any considerable scale by 

 the " Challenger " expedition sent out by the British Government 

 in the seventies, and which explored for four years all the great ocean 

 basins. Since that time many other expeditions have added to the 

 knowledge obtained by the " Challenger." In our country the work 

 of the U. S. Bureau of Fisheries, especially through the numerous 

 voyages of the " Albatross," has resulted in the accumulation of a 

 tremendous amount of material. This has been deposited in the U. S. 

 National Museum, and has been the basis for a considerable amount 

 of literature dealing with the occurrence of the foraminifera, especially 

 of the Pacific, the Philippine region and that of the western Atlantic. 



