NO. 4 FORAMINIFERA CUSHMAN 9 



ocean basins from the continental shelf out into deep water, Globi- 

 gerina-ooze makes up the entire ocean bottom to depths of about 2,000 

 to 2,500 fathoms. Beyond this depth the ocean bottom consists mainly 

 of red clay. The lack of the calcareous foraminifera in such regions 

 is due to their solution under pressure. In red clay areas numerous 

 species which develop arenaceous tests are characteristic, show- 

 ing that deep water conditions are in no wise detrimen'tal to the 

 foraminifera. 



If material is studied from definite regions, such as I have done 

 for the western Atlantic, it will be found that the foraminifera group 

 themselves into definite faunas just as do other groups of animals in 

 the same regions. The distribution of the shallow water species 

 includes the West Indies, the northern and northeastern coasts of 

 South America, the shores of Mexico and Central America and our 

 own coast as far north as Florida or to the latitude of Cape Hatteras. 

 North of this point an entirely new fauna is found. This continues 

 north to the regions of Nantucket, and further north is replaced by 

 much colder water fauna which is Arctic in character. This is very 

 largely determined by temperature. 



The Indo-Pacific shows another fauna which is characteristic of the 

 warmer parts of the Pacific and Indian oceans. A great many species 

 are limited to comparatively shallow water in this region, a few of 

 them extending into the West Indian region. The eastern and western 

 sides of the Atlantic have very diflferent faunas and in general the 

 distribution of species living in shallow water or on continental shelves 

 are as restricted as are those of any other groups. There are two 

 faunas which are widely distributed. These are the pelagic species 

 which are abundant especially in the warmer portions of the oceans 

 like that of the W. Indies and the Gulf Stream, where a very few 

 species occur in great abundance, their empty tests raining down 

 on the sea floor and building up great areas of Globigerina-ooze. The 

 distribution of these species on the ocean bottom is determined almost 

 entirely by surface currents and temperatures. Another group, that 

 which lives normally at great depths, is apparently controlled more 

 by temperature than by depth. As a result many of these species occur 

 in all the ocean basins and in cold shallow waters in the temperate 

 or polar regions. These follow the same laws in their distribution as 

 do those of crinoids and other animals which make their home under 

 similar conditions. Very much has yet to be done in determining the 

 geological distribution of the different species, as the tendency has 

 been in the past for most writers not to make close specific determi- 

 nations. 



