170 THE VOYAGE OF H.M.S. CHALLENGER. 



lateral costae, and appear as irregularly dentate ridges separated by slight depressions. 

 The calicle is compressed from side to side in the centre, so as to be narrowest there. 

 Its upper margin is curved, describing about one-third of a circle. There are six systems 

 of septa disposed in five cycles. The septa, which are extremely thin and fragile and 

 covered with rounded granules, are disposed in rows. The primary septa approxi- 

 mately equal to the secondary, giving somewhat the appearance of twelve systems. 

 These septa are broad and prominent, with a rounded superior margin, and show curved 

 lines of growth very distinctly. The septa of the third, fourth, and fifth cycles succes- 

 sively diminish in breadth, and are thus very markedly distinguished from one another 

 and from the primary and secondary septa. The quaternary septa join the tertiary a 

 short distance before reaching the columella. The septa of the fifth cycle are incom- 

 plete. The margin of the calicle is very deeply indented, the costse corresponding to 

 the primary and secondary septa being prolonged in conjunction with the outer margins 

 of those septa into prominent pointed processes. Similar but shorter costal prolongations 

 accompany the tertiary septa and some of the quaternary. Between each of the sharp 

 projections thus formed the edge of the wall of the calicle presents a curved indentation. 

 The fossa of the calicle is extremely deep and capacious. The columella is elongate, with 

 a nearly smooth surface formed of processes from the bases of the septa. All three perfect 

 specimens obtained were of nearly the same size, and of closely simdar form, being all 

 pinched together towards the centre and showing no tendency to broaden out there, nor 

 to become irregular or to split up into fragments. The two broken specimens are in 

 form, as far as they go, precisely similar to the perfect ones. 



Judging apparently only from the woodcut given in Nature, 1 and without having 

 referred to my paper in the Proceedings of the Eoyal Society, Professor Lindstrom has 

 placed this species with Flabellvm laciniatum. He describes specimens dredged off the 

 Azores in from 200 to 300 fathoms as agreeing with certain descriptions and figures 

 given by Professor Martin Duncan and myself. 2 I can see no resemblance between 

 Professor Duncan's figures cited by him and my own ; nor can I think, after examining 

 specimens of Flabellum laciniatum lent to me by Professor Duncan, that the two corals 

 can be identical. I cannot, however, tell what amount of variation a long series of 

 specimens might show. The large size, extreme lightness and fragility, and the peculiarly 

 curved contours of the deep-sea form seem to be sufficient to separate it specifically. 

 The Challenger specimens were obtained off the Azores also, but from a depth of 1000 

 fathoms. 



With the adult corals were obtained two very small specimens, which seem 

 almost certainly to be the young of the present species. They are in the form of small 

 hexagonal columns slightly expanded above, and showing on each of the six faces a 



1 Nature, vol.viii. p. 400. - G. Lindstrom, Actinology of the Atlantic Ocean, p. 12. 



