GENERA OF FAVOSITIDAL. 107 



recognisable as subpolygonal lines surrounding each orifice, 

 and the thickened margins are adorned with tubercles or 

 ridges arranged in a more or less conspicuously radiate 

 manner round the calices. Septa represented by rows of 

 spinules arranged radiately in vertical rows. Tabulae few, 

 remote, complete. Mural pores few, large -sized, irregularly 

 distributed. 



Obs. This pretty species is readily distinguished from the 

 forms most nearly allied to it by the peculiar ornamentation 

 of the incrassated margins of the calices, which -are ornamented 

 with rows of granules or discontinuous ridges invariably having 

 a more or less clearly recognisable radiate arrangement (PI. V., 

 fig. 3 #) Vertical sections show that the walls of the coral- 

 lites are greatly thickened (PI. V., fig. 3 b}, and that this 

 thickening is rapidly augmented in amount towards the open- 

 ings of the tubes ; but considerable differences obtain in the 

 extent to which this process is carried. In some instances, the 

 thickening is so great that the actual openings of the corallites 

 appear to be separated by dense calcareous tissue to their own 

 diameter or even more ; but in others they are much more 

 closely approximated, owing to the comparative thinness of the 

 walls. Vertical sections (PI. V., fig. 3 b) further show that the 

 walls of the corallites are always distinctly recognisable and 

 closely contiguous, no ccenenchymal tissue being present ; that 

 the visceral chambers remain open throughout their entire 

 length, though greatly contracted in diameter by the thicken- 

 ing of the walls ; that there are a few, remote, horizontal 

 tabulae ; that the septa are represented by rows of spinules ; 

 and that the cavities of the tubes are placed in communication 

 by a few large pores, of the same character as those of Favo- 

 sites, but quite irregular in their distribution. Tangential 

 sections (PI. V., fig. 3 c) show the same thickening of the walls 

 of the corallites as do vertical slices, and show distinctly that 

 this thickening is due to the deposition of successive thin con- 

 centrically-disposed laminae of sclerenchyma within the interior 

 of the tubes. They further show that the actual polygonal 



