78 CORALS 



we are justified in placing them in separate families, 

 but in order to become adapted to the same or similar 

 mode of life they have adopted the same external form and 

 a similar change in habit at the same time of life. 



Both genera are usually found on a gravelly or sandy 

 bottom, in contrast to most corals, which are found on a hard 

 bottom. When they are very small they can be supported 

 on a small shell or stone, but when they are larger and 

 heavier than the stone there is a tendency for them to be 

 overbalanced and smothered in the gravel. The only way 

 to overcome this danger is to become detached from the 

 stone and support themselves as best they can as free 

 corals. We have unfortunately no record of observation 

 made on the hving coral, and it is not possible to hazard 

 a guess as to how this is done, but there can be little doubt 

 that the peculiar compressed cone shape and the variable 

 wing-like side processes in both genera are special adapta- 

 tions for this purpose. 



Another point of interest about Endopachys is that it is 

 probably one of the corals on the verge of extinction. It 

 may have been very abundant in Eocene and later times, 

 and thus have become spread over a wide area in suitable 

 localities, but is now very rare, and shows the common 

 attribute of many rare things, a wide but discontinuous 

 geographical distribution. 



Heteropsammia. — Another example of convergence, 

 but convergence of a different kind, is seen in the Eupsammiid 

 coral Heteropsammia (Fig. ^2). This coral is either solitary 

 or forms small colonies of two or three polyps by fission, 

 but it is very frequently free and associated in its freedom 

 with a small sipunculid worm like the Turbinoliid coral 

 Heterocyathus. 



Both these corals are found on sandy bottoms, sometimes 

 in the Indian Ocean, together or in close proximity, and 

 they have found out quite independently the same dodge 

 for maintaining an upright position in the shifting sand. 



Dendrophyllia. — I), ramea is a large branching coral 

 with a general form not unlike that of Lophohelia. And just 

 as the perforate solitary Balanophyllia is sometimes found 



