MATTHAI— RECENT COLONIAL ASTR^ID/E 85 



a paliform lobe, exsert to about 1 mm., exsert ends usually arched sometimes flat. Costee 

 thin and sharp or thick and flat, serrate or with transversely extending giunulations, 

 those of neighbouring corallites usually meeting in notches along the middle of the 

 perithecal regions, sometimes alternating ; an alternating cycle of smaller costse (usually 

 without corresponding septa) sometimes present. Columella formed of twisted septal 

 trabeculse, sometimes quite dense, from j to J width of calyx. 



Multiplication by unequal or sub-equal fission. 



Towards edge of specimens the corallites often project obliquely, the sides facing the 

 edge projecting more — up to 3 mm. — than those facing the centre of corallum ; the 

 corallites are further apart (up to 4 mm.), with walls thicker, calices shallower, septa 

 thicker and rougher, costee flat and thick. 



Gardiner's examples of Orhicella laxa, Klunz. and Orhicella horradailei, Gard. form 

 a dense variety of the present species, characterised by obliquely projecting corallites with 

 thick walls, well-developed paliform lobes, dense columella and a conspicuous alternating 

 cycle of smaller costse without corresponding septa. Some of the corallites appear to have 

 been formed by budding. In certain regions the corallites have remained in the normal 

 condition (see PL 32, fig. 3). The examples of Favia laccadivica, Gard., show a somewhat 

 crowded appearance of septa within the corallites ; the cycle of smaller costee has rudi- 

 mentary septa, and the exsert ends of the septa are either directly continuous between 

 corallites or meet in shallow notches. One of Gardiner's specimens of Favia cavernosa 

 (Forsk.) has the corallites wide apart up to 7 or 10 mm. (average 3'6 or 4 mm.), not 

 projecting ; the septa and costse are very thin, the latter directly continuous across the 

 intervening perithecal regions and tending to be united by transverse ridges. 



Polyps. (1) Both entocoelic and exocoelic tentacles present. (2) Stomodseal ridges 

 broader than thick and somewhat constricted at their bases. (3) About eleven principal 

 couples of mesenteries present. (4) In the stomodseal region of polyp subsidiary couples 

 of mesenteries about twice the number of principal couples. (5) In the stomodseal i-egion 

 of polyp, entocoelic pleats narrow except in middle of pleatal region, where they are some- 

 times sub-divided, usually constricted at their bases and extending over outer halves of 

 principal mesenteries. (6) Mesenterial endoderm vacuolated to form closely-arranged 

 goblet-shaped spaces, swollen where entocoelic pleats are broader. (7) Convolutions of 

 mesenteries not so abundant as to be massed together in inter-mesenteric chambers below 

 stomodseum, scarce or even absent towards bases of polyps. 



Remarks. A. Polyps. Of the four polyps examined three have each 11 principal 

 couples of mesenteries (4 incomplete), while the remaining polyp has only 10 couples 

 (6 incomplete). Subsidiary couples number 10 — 24, some not extending below the entero- 

 stome ; the members of the same couple are frequently unequal. The convolutions of 

 the mesenteries protrude into the edge-zone and through the oral-disc. The tentacles are 

 often less in number than the entocoeles and exocoeles. The large terminal batteries 

 consist of closely-arranged nematocysts I, each with from 35 to 40 turns of the spiral, and 

 a few II b ; long narrow structures, homogeneously stained pink, are seen in large number 

 in a few of the terminal batteries as in Galaxea fascicularis. Four to six sub-terminal 

 batteries are present, in which large clear oval vacuoles are conspicuous. 



