212 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1917. 



Size of colonies of Favia fragum — averages according to age. 



1 As Nos. 7 and 8 fused, separate measurements of the diameters became impracticable. 



Favia fragum is a species that never attains a large size, between 

 60 and 75 millimeters being about the usual maximum diameter. 



The size of colonies of Poriles astreoides, according to age is given 

 in the following table : 



