4 BULLETIN 71, UNITED STATES NATIONAL MUSEUM. 



Family 7. GLOBIGERINID^. 



Test composed of numerous chambers, usually much inflated, 

 arranged in a trochoid or planospiral coil, often umbilicate, cal- 

 careous and perforate walls; aperture either large and single or with 

 numerous accessory apertural openings. 



This family, while not consisting of a large number of species or 

 genera, is nevertheless one of the most numerous of the present ocean 

 in regard to numbers of individuals and in the deposits of the present 

 ocean bottom. Making up as it does the great proportion of the 

 enormous amount of pelagic foraminifera and composing the great 

 proportion of the mass of the Glohigerina ooze which makes up the 

 most of the ocean bottom between 500 and 2,000 fathoms, its import- 

 ance may be realized. 



Among the fossils it makes up the mass of the various chalk 

 deposits and has a long geological history. At the present time, 

 however, perhaps its greatest interest is in the modifications of the 

 test for pelagic life. 



In order that the greatest amount of surface may be allowed for 

 the bulk of the test, there is a tendency, in the pelagic forms of the 

 family at least, to assume as nearly as possible a spherical form. 

 The chambers individually assume a spherical contour, and even 

 when made of several chambers the whole test in the various genera 

 tends to take on a subspherical outline. This is carried to perfection 

 in Orbulina, where the final chamber is a perfect sphere. In the 

 pelagic forms the protoplasm is protruded from the test and forms 

 a vesicular mass about the exterior. This is probably aided some- 

 what by the long radiating spines which are usually present in fresh 

 pelagic specimens. In order that the protoplasm may have free access 

 to the exterior, the apertures in this family are as a rule large, espe- 

 cially in pelagic species; where they are not large they are often 

 numerous, as in Candeina. In Glohigerina the apertures from several 

 chambers may enter upon a common umbilical cavity, or in the 

 higher development, as in G. conglohata, sacculifera, etc., there are 

 numerous accessory apertural openings so that there is a large 

 amount of space allowing perfectly free communication with the 

 exterior. 



The surface of the wall of the test is very characteristic in many 

 species, consisting of a reticulated pattern with the pores at the base 

 of the depressions. 



The distribution, especially of the pelagic species, is world-wide, 

 but seems to reach its greatest development in the warmer waters of 

 the oceans. 



