MADREPORARIAN CORALS 327 



the greater compression. The outside of the column is largely covered by growths of 

 Polyzoa and one end of the caHce has been broken and regenerated. There are about 

 16 growth rings on the epitheca. 



Flabellum curvatum Moseley (PL XX, figs, i, 2). 

 'Challenger' Rep. p. 174, VI 2 (1881). 



The series comprises 159 specimens dried, and a number in spirit, well preserved. 



The polyps show a deep purple rim round the peristome where the tentacles rise, the 

 other parts being less coloured ; the pigment is gradually soluble in alcohol so that the 

 whole polyp may be lightly coloured. The tentacles are tightly set with nematocysts at 

 their ends and are found over all septa except those of the last formed cycle. 



The corallum is a flattened cone with no side wings; it becomes detached from its 

 original support and lies freely on the bottom. The calicular opening is about 100 to 65, 

 length to breadth. The epitheca usually shows transverse growth ridges. 



The rim of the epitheca forms a slight upstanding wall above the edges of the septa, 

 which never rise above it. In the smaller specimens 12 equal septa regularly fuse by 

 trabeculae to fill in the central valley of the calice at about half its depth. In larger 

 specimens septa III are usually joined to these, but are narrower and thinner, their 

 trabeculae extending inwards at a deeper level. In median-sized forms four cycles of 

 septa are present, but in larger specimens septa V appear and, when this cycle is com- 

 plete, 1-4 or more pairs of VI may form, usually near the directives. Growth ridges 

 are distinct on the septal sides and are set with spines ; the result is a rough appearance 

 of the septa, the edges of which may show fine serrations. 



Every individual coral varies in its axial valley, the trabecular floor of which usually 

 lies at a depth of one to two-thirds the height of the corallum. Septa I and II slope to 

 this level almost perpendicularly, and the false columella formed by their trabeculae 

 varies greatly in breadth and coarseness of structure ; its formation is very little assisted 

 by extensions from septa III. 



The extreme height of the specimens is 48 mm., calicular length 36 mm. While 

 plenty of specimens show curving, this is never as extreme as in Moseley's eight 

 specimens which were dredged at 600 fm. off the Rio de la Plata. The external decompo- 

 sition of the epitheca is as Moseley described, and this makes visible the septa below as 

 ridges down the same. 



The wide distribution of these corals shown below suggests that we are dealing with 

 a definite species, the variation of which will now be clear. There may be several 

 synonyms, previously described species, or it may be a synonym of one of these, but no 

 such relationship is clear. 



Localities: St. WS 76, 207-205 m., i, 20 mm. high by calice opening 22 x 15 mm., 

 12 septa solidly fused in centre, cycle V almost complete: St. WS 80, 152-156 m., 

 I large and 2 small: St. WS 83, 137-129 m., 3, with calices 17, 16 and 12,^ in larger 

 cycle V considerably developed: St. WS 85, 79 m., 3 young: St. WS 92, 145-143 m., 



1 Such single measurements are the maximal along the calicular opening. 



