FORAMINIFERA 



CHAPTER I 



THE LIVING ANIMAL 



The foraminifera are almost entirely marine animals, a very- 

 few living in brackish or even fresh water. They are single 

 celled animals belonging to the Protozoa. Except for a few of 

 the simplest types, there is developed a test, either of agglu- 

 tinated foreign material, or chitin, or of calcareous material 

 secreted by the animal itself. These tests are preserved as fos- 

 sils in many of the geologic formations since Cambrian time. In 

 the existing oceans, foraminifera occur in enormous numbers, 

 and in water from the continental shelf out to about 2,000 

 fathoms or more their tests form the thick Glohigerina-ooze of 

 the ocean floor. As fossils they are often very abundant, and in 

 the Palaeozic as well as in the younger formations they have 

 formed thick limestones. The great pyramids of Egypt are con- 

 structed from limestones made largely of fossil foraminifera. 

 In the tropics, the sands of the beaches are often largely com- 

 posed of the tests of foraminifera, and in shallow water their 

 great numbers actually form obstructing shoals. 



Most of the abundant living species are of small size except 

 in the shallow waters of the tropics where numerous species of 

 considerable size still exist. In the Eocene and Oligocene, 

 species with large tests several inches across were developed. 

 There is but a single living species, now found in the Indo- 

 Pacific, which has as large a diameter as those of the earlier fos- 

 sils, and this species has a very thin discoid form. 



Species have definite geologic and geographic rangeSj^jand 



uj 1 L I B R A R Y j ; 

 \<^\ / V 



