21 8 TABULATE CORALS. 



internal structure, S. geniculata, Phill., agrees entirely with 

 S. reticulata, and it is unnecessary to dwell upon the pheno- 

 mena exhibited by thin sections. There is, however, one 

 curious character, of very common though apparently not uni- 

 versal occurrence, in which 5". genictdata is quite peculiar. One 

 of the most striking features, namely, in 6". geniculata, is the 

 apparent thickness of the walls of the tubes ; and thin trans- 

 verse sections show that this is really due to the fact that the 

 proper wall is liable to become lined by a dense, finely-lamin- 

 ated secondary deposit of sclerenchyma (see PI. X., figs. 4 a 

 and 4 b). This secondary deposit is of a markedly darker 

 colour than the true wall, which, along with the short spini- 

 form septa, can be thus easily recognised. In this peculiarity, 

 ►S. geniculata, Phill., bears to the ordinary forms of Syringopora 

 the same relation that Pachypora and its allies bear to Favosites. 

 This same thickening can often be recognised in long sections 

 (PI. X., fig. 4), but I have not been able invariably to recognise 

 its existence, and I am disposed to think that it is probably 

 present only in certain parts of the tubes (as is the case in 

 Pachypora and in some related forms), or that it depends 

 upon age. 



Formation and Locality. — Common in the Carboniferous 

 Limestone of Shap, Kendal, Asby, Ravenstonedale, and other 

 localities in Westmorland. 



