i88 CORALS 



globular cluunbers or other straight tubes with whieh they 

 fuse, the cavities becoming continuous " (I'igs. 87, p. 179, 

 and 95). 



" All the walls are uniformly perforate, but the external 

 surface differs in appearance in places, being sometimes 

 quite smooth and elsewhere bearing minute denticles either 

 sparsely or more closely set. There also seem to be definite 

 larger openings to the exterior." ^ 



The genus Ramulina was founded by Rupert Jones in 

 1875, and seems to have a w^orld-wide distribution in depths 

 of 50-700 fathoms of water. 



PoRiFERAN Corals 



Merlia. — Among the many encrusting calcareous 

 organisms that have for a time puzzled the experts there is 

 no one more interesting and remarkable than Merlia 

 normani (Fig. 96). 



At first it was thought to be a Pol^'zoon, then certain 

 characters were discovered which suggested the view that 

 it was a Foraminifer, but it has at last settled down into 

 a position among the Sponges, where it must remain until 

 some unexpected evidence is forthcoming to prove that it 

 has been wrongly classified. The first specimens to be 

 discovered were found in sixty fathoms of water off Porto 

 Santo Island near Madeira. They consisted, when dry, of 

 an encrusting calcareous substance covered by a thin yellow 

 pellicle. 



On examining sections of this substance siliceous pin- 

 shaped spicules were found in the upper layers, and conse- 

 quently it was suggested that the yellow pellicle was the 

 remains of a sponge which had grown over and perhaps 

 smothered the organism that had formed the calcareous 

 substance. 



It is well known that in the Order of the Sponges (Porifera) 

 one group of genera forms calcareous spicules and another 

 siliceous spicules, but it was considered to be very unlikely 



^ Dakin, Reports on Ceylon Pearl Oyster Fisheries, 1906, v. p. 228. 



