GEOGRAPHIC DISTRIBUTION 39 



to the coast of Ireland. In the Pacific there is a general fauna 

 covering the region from Africa to the Polynesian Islands. Many- 

 things are lacking in the western portion which may be 

 separated as an East African fauna and the other kept as an 

 East Indian fauna including Polynesia, running northward to 

 southern Japan and including Hawaii where many of the 

 characteristic things are again lacking. It is possible to draw 

 lines more closely and find a number of smaller faunas in this 

 general area. 



With the foraminifera, it may be said that temperature is 

 the great controlling force, and depth except as controlled by 

 temperature a much smaller factor. 



The most abundant single deposit of foraminiferal origin 

 today is Globigenina-ooze. It is made up of the tests of the 

 pelagic foraminifera of the Globigerinidae and Globorotaliidae 

 and is formed in the ocean basins from 500 to 2500 fathoms in 

 depth. There are many other groups represented especially 

 from 1000 fathoms up, but these two families greatly 

 predominate. 



In abyssal depths where it is difficult for carbonate of lime to 

 accumulate, many arenaceous forms are found. This is not due 

 as seems to be a current opinion because they are found only in 

 such habitats, but that they are the only ones that can persist 

 under the particular conditions. If an equal amount of 

 Globigerina-ooze were treated with weak acid, it would probably 

 be found that the residue would be richer in arenaceous forms 

 than the red clay areas of greater depth. Arenaceous forms are 

 abundant often in rather warm shallow waters although certain 

 forms become very abundant in shallow cold waters. It is the 

 rule in cold waters in other groups as well as in the foraminifera 

 that the number of species is few but the individuals occur in 

 enormous numbers. 



The Lagenidae as a rule are characteristic of the continental 

 shelf and from 50 to 500 fathoms are very abundant. The 

 Miliolidae are most abundant in shallow warm water of coral 

 reef regions, but Pyrgo has become adapted in a number of 

 species to deeper colder waters. The larger foraminifera of the 

 families Camerinidae, Peneroplidae, Alveolinellidae, Calcar- 

 inidae, etc. are almost exclusively tropical in waters under 30 

 fathoms. The approximate depth of many Tertiary sediments 



