POUITES FROM NO KECOKDED LOCALITY. l2l 



the only change in structure is that the walls are much lower, and have lost their delicate 

 membranous character. 



The coral is of a cold, dull grey colour. 



The two specimens differ in minor details, but the chief characteristics, the raised walls, 

 and the convoluted surface they have in common. In h the convolutions are less marked than 

 in a, and the walls are not so thin and delicate. 



These are clearly Indo-Pacific forms, and may have formed part of Mr. J. J. Lister's 

 collection from the Tonga Islands, the bulk of which was described in Vol. V. pp. 34 to 41. 



a. With very thin, high walls. Zool. Dept. 1906. 1. 1. 16. 



h. Zool. Dept. 1906. 1. 1. 17. 



116. Porites x. 14. (Porites incertoe sedis quartadecima.) (PI. VII. fig. 6.) 



[British Museum.] 



Description. — The corallum rises as a flat-topped, pear-shaped mass, with rather smooth 

 surface, and closely encrusting edges extending downwards 5 cm. 



The calicles are composed of open, delicate i-eticulum, about 1 • 25 mm. across. The walls 

 are mostly raised as a thin, nearly straight thread, sometimes quite smooth and conspicuous, 

 at others, broken up into minute spiky granules. Within the wall there is a ring of septal 

 granules joined by delicate, glassy synapticula?, the septa being also delicate threads. Tlie 

 pali are normal, and rise as slightly longer, spiky or frosted granides. They all rise from an 

 open, reticular, thread-like tangle, from which a small, often flattened, columellar tubercle also 

 rises. The openings between the delicate skeletal elements are large, enabling one to look 

 down into the coral. 



The section shows a very compact arrangement of fine, glassy, uneven trabeculae, which 

 ri.se as a dense forest of small spiky or frosted granules. 



The figure is taken from the flat top of the stock, where the growth is purely reticular 

 and not trabecular. On this account there are no granules. The specimen almost certainly 

 belongs to the group P. Tonga Islands .^ to 7 (see Vol. V., pp. 36-38). The characters are 

 especially interesting here in contrast with those of the West Indian forms. 



a. Zool. Dept. 1906. 1. 1. 18. 



117. Porites x. 15. {Porites iivcertm sedis quintadedma.) (PI. VII. fig. 7.) 



[British Museum.] 



Description. — The corallum is glomerate, with convoluted surface ; the ridges being 

 low and flat-topped, or slightly ridged, separated by shallow, irregular valleys. The living 

 layer is confined to the top of the mass, extending only 2 to 3 cm. down the .sides. 



The calicles are all slightly pitted, so that the walls trace a low network over the surface. 

 They vary in size, averaging 1 mm. They open in a delicate, filamentous reticulum. The 



