OF THE MERGUI ARCHIPELAGO. 



7 



Poltctathus difficilis, sp. nov. (Plate I. figs. 17, 18.) 



The colony covers considerable space and encrusts ; the coral- 

 lites are short, cylindrical, crowded in places, distant in others, 

 broadest at the calice. Calice circular in outline. Septa in three 

 cycles, the tertiaries uniting with the secondaries ; the prima- 

 ries are the larger and are slightly exsert, and all are granular 

 at the sides ; they are unequal in size, and project into the 

 calice, and have trifid spinules on the edges. Columella small, 

 concave, and formed by little processes united at their bases. 

 Pali small and short, often indistinct, small before the primaries 

 and larger before the secondaries and nearer the calicular edge. 

 The costae are large, broad, subequal, and reach over the basal 

 structure more or less, distinct, close, and sometimes curved 

 or bent suddeuly, much broader than the septa. A granular 

 epitheca. Much of the basal structure is non-costulate, but is 

 granular. 



Height of corallites 2-3 millim., breadth of calices 2-3 millim. 

 Locality, Mergui Archipelago. 



Family Pocilloporidj;, Dune. {Rev. p. 46). 

 Genus Pocillopora, Lmk., pars. 



POCTLLOPORA CESPITOSA. 



Pocillopora caespitosa, Dana, U. S.Expl. Exped., Zooph. vol. vii. p. 525, 

 pi. 49. figs. 5, 5 a, 1846. 



Locality, King Island Bay. 



Pocillopora favosa. 



Pocillopora favosa, Ehrenberg, A bhandl. d. ATcad. Berl, (1832) p. 351 

 1834. 



Locality, Sullivan Island. 



Family Aste^idj. 

 G-enus Mussa, OJcen. 



MlISSA CRISTATA. 



Madrepora cristata?, Esper, Pjianz. t. i. p. 150, Madr. p. 226, 1791. 

 Mussa cristata, Ed. 8f H. Hist. Nat. des Cor all. t. ii. p. 335, 185/. 

 Locality, Elphinstone Island, below low-water mark. 



Mussa flextjosa. 



Mussa flexuosa, Ed. H. Ann. des Sc. Nat. 3 ser. t. xi. p. 252, 

 1849. 



Locality, King Island Bay. 



