FORAMIN1FERA. 115 



of the Gldbigerinida are included by Dr Carpenter all those 

 hyaline or vitreous Foraminifera which have their shell- 

 substance coarsely perforated for the exit of the pseudopodia. 

 There is sometimes, though not usually, a " supplemental " 

 skeleton, and the chambers generally communicate with one 

 another by a larger or smaller crescentic aperture, and not 

 by circular pores. Three simple or unilocular types viz., 

 Orlulina, Ovulites, and Spirillina, are known ; of which the 

 first (fig. 14) is the most important. It has a spherical 

 shell, with numerous large -sized pores distributed among 

 the smaller ones ; and though its distribution at the present 

 day is universal, its earliest appearance seems to be in the 

 Miocene Tertiary. In Ovulites 1 the one-chambered ovate test 

 possesses an aperture at both ends. It is found in the 

 Eocene and Miocene. In Spirillina, again, the test is coiled 

 into a flat spiral ; and, likewise commencing in the Eocene, 

 it is continued to the present day. The type of the Globi- 

 yerinida, however, is Globigerina itself (fig. 18, &), in which 

 there is a polythalamous shell consisting of globose segments 

 arranged in a turbinate spiral, or irregularly disposed. The 

 chambers do not communicate with one another directly, but 

 each opens by a special aper- 

 ture into a deep central or um- 

 bilical depression. In some 

 forms (as also in Orlulina) 

 the test, when perfect, ap- 

 pears to be covered with long 

 and extremely delicate spines. 

 Globigerina dates from the 

 Cretaceous (Trias?), and is 

 extremely abundant. It is of 

 special interest, as being the principal constituent of the 

 " ooze " found at great depths in the larger oceans at the 

 present day ; while its shells form an equally large portion 

 of the White Chalk (see p. 15). 



The remaining members of the Globigerinida fall into two 



1 Recent researches point to the view that Ovulites is a detached segment of 

 a calcareous Alga, but further evidence is required before this conclusion is 

 finally adopted. 



