OE,IGrZnNT^_IL. ARTICLES. 



» 



I. A R.EHAEKABLE OaBBONIFEEOUS CoEAL. 



By R. G. Caeeuthees, F.G.S., Geological Survey of Scotland. 



(PLATE XI.) 



AMONGST the Carboniferous corals, not the least interesting are 

 those species which, for one reason or another, may be difficult 

 to classify, or at any rate diverge somewhat from the common order. 

 It is with one of tbese aberrant members that the present 

 communication is concerned ; and it is, perhaps, not altogether 

 unfitting tbat most of the material happens to be of Irish origin. 



The peculiarities under review are essentially of a developmental 

 nature : as a preliminary, therefore, it is as well, even at the risk of 

 needless repetition, to outline the normal order of septal development 

 characteristic of the Rugosa in general. 



Figl 



F'g 2 



O 



Fig 4 



CL CL 



Fig 5 



Development of the major septa in a normal Rugose Coral (Figs. 1-3) and 

 Cryptophyllum (Figs. 4-6). H, main or cardinal septum; A, alar septum; 

 CL, counter-lateral septum ; G, counter septum ; a, b, c, etc., metasepta. 



The initial growth-stages of a Rugose coral are frequently obscured? 

 for it is obvious that if the basis of attachment be relatively large 

 there will be a corresponding increase in the number of septa first 

 seen. In the most favourable circumstances, the first stage shows 

 a single septum (the "axial septum") stretching across the diameter 

 of the corallum from wall to wall (Diagram, Pig. 1); later on this 

 separates into the main and counter primaries, opposite one another. 

 At each end of the axial septum a pair of new septa then appear, 



