FORAMINIFERAN AND OTHER CORALS 185 



but the great majority of these encrusting Foraminifera do 

 not attain to a size of more than a milHmetre or two in 

 diameter and need not, therefore, be referred to in detail. 

 There is, however, a variety of Gypsina plana which reaches 



Fig. 93. — Gypsina. Gypsina plana. In-oin Mauritius, loo fathoms. Nat. size. 



such a gigantic size — for a Foraminifer — that it might well 

 be mistaken for a coral of another Order. 



Like other Foraminifera the substance of Gypsina plana 

 is built up of minute 

 chambers with walls per- 

 forated by the foramina, 

 and when the young free 

 form becomes adherent 

 to a stone the chambers 

 increase in numbers at 

 the circumference and by 

 the formation of laminae 

 after laminae of new 

 chambers growing over 

 the surface of the old 

 ones (Fig. 94). In some 

 specimens obtained by Prof. Stanley Gardiner in deep 

 water (25-100 fathoms) in the Indian Ocean these laminated 

 masses of Gypsina have formed a thick crust entirely 

 surrounding their original support, and have the appearance 



'•o^Oi><^: 



Fig. 94. — Vertical section of Gypsina plana 

 showing the perforated chambers. From a 

 drawing In' Miss Lindsev. :■: 120 diams. 



