Lopliophylliiin and Cyathaxonia. 55 



The tabulae of Cyathaxonia do not contribute in any way towards 

 the construction of the columella ; they remain uniformly thin right 

 up to their connexion with the latter, and never show any trace of 

 passage into that structure. The columella of Cyathaxonia is therefore 

 developed at a very early stage, and it is built up round an imaginary 

 central axis, remaining throughout quite independent of septa or 

 tabulae, although these are in complete contact with it. In 

 Dr. Vaughan's species, C. rushiana, the columella is relatively larger 

 than in C. cornu, and in transverse sections shows a marked elongation 

 in line with the cardinal fossula. This is occasioned by the radiation 

 of the crystalline fibres from an imaginary line instead of a point; 

 this ' line ' is usually either darker or lighter than the rest of the 

 columella, although occasionally no colour differentiation can be seen. 

 "With the exception that most specimens are three or four times larger 

 than C. comu, there is no further difference between the two species, 

 and all gradations can be found between them. 



2 ^--^.3 4- 



Diagrammatic representation of vertical sections cut down septa, in the cardinal- 

 counter septal plane, illustrating the formation of the columella in 

 Lophophyllum and Cyathaxonia. Thick lines indicate growth region ; 

 thin lines, direction of crystalline fibres. 

 Fig. 1. Zaphrentis omaliusi. 

 ,, 2. Zaphrentiseruca [Lophophyllum B:Vi(i\,%.). 



" ,■ [Lophophyllum (Koninckophyllum auctt.). 

 ,, 5. Cyathaxonia cornu. 



Septa. — Both C. cornu and C. rushiana have very long minor septa, 

 which appear at a very early period, when perhaps only seven or 

 eight major septa have developed. These minor septa all lean inwards 

 away from the cardinal fossula, and each one ultimately fuses with 

 a major septum ; the pair in the counter fossula (one on each side of 

 the counter septum) are longer than the rest (PI. Ill, Figs. 4, 9, and 

 10) and invariably appear first, sometimes before the conclusion of the 

 protoseptal stage, with six primary septa. The)'- are not formed by 

 a splitting of the major septa, but are minor septa in the strict 

 morphological sense, as is shown by their development and by their 

 relation to the vertical furrows on the epitheca. On examining 

 a good specimen it will be noticed that each alternate furrow coincides 

 with one of the longer series of septa, and each furrow between 

 corresponds to one of the shorter series. The latter are therefore the 

 minor septa, this rule holding good in all Rugose corals. The 

 remarkable length of the minor septa, and their general disposition, 

 frequently aid in the recognition of these two species, especially 

 when silicification has obscured the columella. 



