IQO 



CORALS 



W'licn the surface of the coral is examined with a lens 

 it is seen to be perforated by a number of cylindrical tubes, 

 and between these tubes the calcareous walls rise up in 

 polygonal ridges which are ornamented with columella-like 

 tubercles where the angles of adjacent polygons meet (Figs. 

 97 and 98). 



If the specimens are sufficiently well preserved to show 

 these tubercles they present a surface character which is 

 quite sufficient to distinguish Merlia from any other coral, 

 but of course this character is the first to disappear if the 

 specimens are water- worn. 



Fig. 97. — Meilia normani. Photo of a vertical section through a fragment of 

 a specimen from Solomon Island showing the vertical tabulate tubes of which 

 it is composed. < 15 diams. 



On examining a vertical section or fractured edge of a 

 specimen the most interesting character is seen in the 

 presence of a series of fiat tabulae dividing the cavity of 

 the vertical tubes into a number of chambers or " crypts." 

 Merlia is therefore a tabulate coral. The tabulae, however, 

 differ from the usual form of tabulae in the fact that they 

 seem to be always perforated in the centre by a little round 

 hole of communication between two adjacent crypts. 



The investigation of fresh material has shown that the 

 sponge which forms this remarkable skeletal structure 

 belongs to the Family Haploscleridae and the Order Mon- 

 axonellidae, but its most curious character is that certain 



