SOLITAKY COKALS. 197 



30 millims. in height. The longer axis of the calice measures 16 milium, the shorter 

 axis 8 millims. ; the small scar at the hase 4 millims. x 2 millims. ; thus the ratio of 

 the axes is 2:1, agreeing with Semper's description. The corallum is compressed, 

 with rounded directive edges, whose sides form an angle of 23 in the dry specimen, 

 but a considerably wider angle in the decalcified specimen. The wall is constricted 

 at tolerably regular intervals and there are three short and stout spines at varying 

 heights on the directive faces, and two short and corroded spines near the basal scar. 

 The costse, especially those corresponding to the principal septa, are distinct and are 

 recognisable nearly down to the basal scar. The corallum is tall, and the directive 

 margins of the calice are nearly level with the lateral margins. The fossa is very 

 deep (6 millims.), narrow and slit-like. The parietal columella is formed by the union 

 of trabeculae given off from the lower ends of the principal septa. There are in all 

 sixty-six septa ; the primaries and the secondaries are of equal size and unite in the 

 columella. The twelve tertiaries are nearly equal in size to the primaries and 

 secondaries and also join the columella. The fourth cycle septa are short, excepting 

 those nearest the two directive septa at opposite ends of the long axis of the calice ; 

 these are nearly as large as the tertiaries and join the columella. Fifth cycle septa 

 are developed in the chambers between the primary and secondary septa on both 

 sides of the two directive septa, and are equal in size to the lateral tertiary septa. 

 In one chamber nearest to a directive, two sixth-cycle septa are developed, one on 

 either side of a quinary septum (see fig. 3a). (This interpretation of the septal 

 succession differs from Semper's, who explained an exactly similar arrangement by 

 supposing that additional second-cycle septa were developed in each of the terminal 

 systems, but it is clear that what he describes as additional secondary septa are 

 nothing more than third-cycle septa, which have grown to the same size as the 

 primaries and secondaries.) The result of this arrangement is that there appear 

 to be sixteen ternary systems, and, in addition, two small septa in one of the 

 systems. The principal septa have very slightly arched, or nearly horizontal, upper 

 edges ; their inner edges descend vertically to the columella, and they are distinctly, 

 though slightly, notched near their insertions on the wall. The surfaces of the septa 

 are thickly covered with fine spinose granules, which have an obscurely radial 

 arrangement. The dry corallum is brilliantly white in colour, and the lower five- 

 sixths of the wall is encrusted by a secondary calcareous deposit, which, on 

 decalcification, proves to be formed by interlacing algal filaments, as described by 

 Fowler for F. patagonichum (14). It is noteworthy that the costae are more 

 conspicuous in the region of this secondary deposit than they are at the upper end of 

 the corallum. 



These Ceylonese specimens are so similar in all respects to the figures and 

 description of Semper's F. irregulare that there can be no doubt of their identity. 

 According to Gardiner (22), F. irregulare, Semper = F. ruhrvm, Quoy and 

 Gaimard, and there is certainly some resemblance between his (not wholly satis- 



