158 
THE OCEAN WORLD. 
found in some of the oldest geological strata. They are essentially 
marine animals, there being nothing found in fresh water at all re- 
sembling them. 
The Astrea are inhabitants of the Indian Ocean, where they are 
found in a great variety of forms, which has led to their subdivision 
into many genera by Messrs. Milne Edwards and J. Haime. The 
animals are short, more or less cylindrical, with rounded mouth placed 
in the centre of a disk, covered with a few rather short tentacula; 
the cells are shallow, with radiating lamella) in Astrea pundiferci 
(Fig. 70), forming by their union a many-formed polypier, which often 
encrusts other bodies. In short, this polype may be described as a 
parasite, for it generally attaches to some other bodies, and it is by 
no means unusual to meet with shells attached to shells. 
The Meandrina differ from the Astreas in having the surface 
hollowed out into shallow sinuous elongated cells, furnished on each 
side of the mesial line with hooked lamella;, ending against one or 
Fig. 71. Meandrina cerebrifonnls (Lamarck). 
