i86 CORALS 



of lum])s of water-worn coral reaching a size of 3-4 inches in 

 diameter. 



The general appearance of these large encrusting forms of 

 Gypsina is much like that of some other corals of a similar 

 habit described in this book, and the occurrence of Fora- 

 minifers of this size is so extremely rare that it would not 

 be surprising if a collector of corals in general were to make 

 a mistake in classifying them. A few notes may therefore 

 be written to describe the principal characters by which 

 they can be recognised as Foraminifera. 



The surface of the coral when magnified exhibits a 

 number of closely fitting and slightly convex areolae varying 

 in size from 70 to 230 microns [i.e. -07- -23 mm.). These areolae 

 representing the outer walls of the chambers of the superficial 

 lamina are perforated by numerous foramina. They might 

 be thought to be the walls of the zooecia of a calcareous 

 Polyzoon, but they differ from them in the absence of the 

 large aperture or orifice for the protrusion of the Polyzoan 

 polyp. 



The only other kind of coral for which they might be 

 mistaken would be the calcareous algae, but the surfaces of 

 the calcareous algae have either no areolae (cf. Halimeda, 

 p. 210), or if they show in some places convex areolae (cf. 

 Fig. loi, facing p. 201), these areolae are not pierced by 

 more than one foramen. 



There is one more point of interest about these large 

 specimens of Gypsina plana. They are so much bigger than 

 the specimens of Gypsina (not exceeding 1-2 mm. in diameter) 

 with which the student of the Foraminifera is most familiar, 

 that it may seem remarkable that they have not been 

 relegated to a distinct genus. 



Fortunately, however, it has been possible to examine ^ 

 a large number of specimens from the smallest to the largest, 

 and it has been found that not only is there a fairly complete 

 series as regards the size of the specimens (i-ioo mm.), but 

 also as regards the size of the constituent chambers (20-230 

 microns). 



* M. Lindsey, Transactions of the Linnean Society of London, vol. 16, 

 1913- 



