MATTHAI— RECENT COLONIAL ASTR^ID^ 73 



Oorallum. Incrusting, tending to be massive, somewhat convex, not rising into 

 hillocks. Corallites more or less circular in outline, not projecting. Walls up to 3 mm. 

 thick, somewhat perforate, neighbouring ones fused with a shallow groove in the middle. 

 Calices from 8 — 10 mm. in diameter, shallow, varying from flat to 2 mm. in depth. 



Septa in two orders, both entocoelic, each consisting of 12 — sometimes a few exoccelic 

 tertiaries up to 7 (in one corallite 14) — highly exsert about 2 mm. ; sides tuberculated, often 

 perforated ; edges with 4 — 8 bluntly pointed teeth, the longest representing the most 

 exsert part of septum ; outer half or two-thirds of septa much thicker (up to 1 mm.) 

 swollen in thecse, thinning out within calices ; primaries usually thicker and somewhat 

 more exsert than secondaries, both meeting columella ; tertiaries when present thinner, 

 of varying width, 1 — 3 sometimes reaching columella, edges usually curving towards 

 and fusing with sides of adjacent secondaries. Exsert ends of septa arched, with bluntly 

 pointed teeth. Costse, also with blunt teeth, either continuous from corallite to corallite 

 or alternating, when continuous with a distinct notch over inter-corallite furrows ; in 

 overhanging edges of corallum, thinner than exsert ends of septa, sometimes very thin ; 

 exocoelic costee present alternating with the main ones. Columella circular in outline, 

 thick, from a third to half the diameter of calices, from upper surface appearing fasciculated, 

 formed of twisted trabeculee from septal margins, in some corallites terminating in upright 

 rods. Calicular dissepiments sloping into columella at an angle of 35°, about 1 mm. apart. 



The perforate walls, shallow calices, stout twisted columella and thick exsert toothed 

 septa give the corallum an unique appearance. Smaller corallites formed by budding are 

 intercalated between the larger ones. Corallites at the margin of the corallum have 

 thinner septa which pass over its edge as costse and loosely trabecular columellse. 



In the sections of the corallum the septa appear to be continuous from corallite 

 to corallite, but this continuity is really secondary, as in the young corallites the costal 

 surfaces are demarcated off". The perforate wall seems to be formed by the perithecal 

 deposit uniting here and there the peripheral thickened septal parts. The peritheca 

 is without any dark centres and hence appears distinct from the septal " trabeculse." 



Polyps. Large, almost circular in outline, about 8 mm. in height, closely aggregated 

 with narrow edge-zones and no coenosarc. Oral-disc much narrowed, about 2 mm. wide 

 in the retracted condition. Mesenteries constituting two complete cycles, each of 

 12 couples. Outer skeletal attachments of some of the mesenteries of neighbouring 

 polyps tending to unite, hence appearing to be continuous from polyp to polyp. The 

 mesenteries with filaments containing nematocysts II and III in their coils, primaries 

 meeting stomodseum*. Tentacles as in genus ; well developed terminal batteries present 

 with closely packed nematocysts I and II h interspersed ; also sub-terminal batteries 

 (number doubtful). Stomodteum laterally compressed. 



Remarks. A. Polyps. The histology of the polyps could only be imperfectly 

 studied owing to partial maceration of their tissues. The ectoderm of oral-disc is thick 

 with narrow diverging tracts containing nuclei in the centre ; granular and mucous vacuoles 



* It is possible that the presence of twelve couples of primary mesenteries in the adult polyps may be due 

 to six couples of secondaries having grown and met the stomodseum; if so the twelve secondary couples in that 

 stage would be tertiaries, but this can be settled only by examining young polyps which were not available. 



SECOND SERIES— ZOOLOGY, VOL. XVIL 10 



