SUBDIVISIONS OF ACTINOID POLYPS. 65 
Another range of forms is represented by the following 
figure of one of the Meandrine corals, already reterred to as 
often called ‘‘ Brain coral.” In the figure, the coral is re- 
duced one-half lineally. The difference between its mode of 
formation and that of an Astraea, has been stated on page 59. 
This species is common at the Bermudas, where it grows to a 
diameter of three feet. It is also found in the West. Indies. The 
ridges in this species are double, and hence the name Diplorza, 



















































































DIPLORIA CEREBRIFORMIS, E. anp H. &K} 
from the Greek for double. A view of part of a living speci- 
men of a related species is shown on Plate IV. A common 
large West India species of Brain coral is called Meandrina 
labyrinthica. 
Still other forms of the Astrzea tribe are foliaceous, or such 
as would result if the growing margin of an Astreea, or of a 
Meeandrina, were to spread out into folia instead of thickening 
upward in the ordinary way. The groups of gracefully cury- 
