64 R. G. Carrutlwrs — A Revision of some Carboniferous Corals. 



and are intimately fused together. They do not quite reach the 

 centre of the calicinal floor, where there is consequently a small 

 tubular area about 2 mm. in diameter, forming the inner end of the 

 fossula. This small tabula is, however, not often found preserved, 

 and in that case the centre of the calyx presents a smooth-walled 

 tubular space (see PI. V, Figs. 5, ba). 



The tnitior sejita ai'e entirely rudimentary. They are seen around 

 the interior of the calyx as low ridges between the thickened bases of 

 the major septa ; those on either side oi the counter septum are 

 sometimes longer than the others. 



The (cardinal) fossula, unlike that of most rugose corals, lies on the 

 concave side of the corallum ; ^ it is always very distinct, extending to the 

 centre of the calyx, and, especially in young specimens, often beyond. 

 Th# outline is continuous and even, becoming sometimes slightly 

 narrower midway in its length, and having a marked expansion at the 

 inner end (1*1. V, Fig. ba) ; although so smooth, the bounding walls 

 are purely septal, and there does not seem to be any accessory 

 thickening, as in Z. koninchi. Good figures of the calyx are given 

 both by Milne-Edwards & Haime and by de Koninck, although in 

 that of the latter the perspective is somewhat faulty. Both figure 

 specimens in which the central tabular area is preserved, so that the 

 fossula appears much narrower and shorter than it does in PI. V, 

 Fig. 5rt (where the tabular area has been destroyed), or than it does in 

 transverse sections. 



Average dimensions. 



Height of an adult specimen, 2"5 cm. ; diameter of calicinal rim, 

 rs cm. ; number of major septa with above diameter of calyx, 27; 

 depth of calyx, 1 cm, 



Inieknal Chakactees. 



(a) Transverse Sections. — The mode of septal arrangement does not 

 differ greatly from that seen in the calyx, though the curvature of 

 the septa convex to the fossula is more clearly shown. In the lower 

 part of the coral it is common to tind the fossula relatively wider and 

 larger in every way than in the upper sections, and expanding 

 continuously from the wall to the centre of the coral (PI. V, Figs. 6^ 

 and 7). The cardinal septum is long and thin, completely dividing 

 the fossula till just below the calyx, whei'e it rapidly dwindles in 

 length. There is never any indication of a counter fossula, nor is the 

 counter septum of itself in any way differentiated from its neighbours. 



The minor septa are extremely rudimentary. They may be barely 

 perceptible, even in calicinal sections of a mature individual, but 

 occasionally those on each side of the counter septum are more 

 jirominent than the rest, affording useful evidence in the identification 

 of that septum. 



(b) Vertical Sections. — The simple tabiilae, arched in the centre, 

 from 1 to 2 mm. apart, and with a strong depression at the fossula, 

 call for no special remark. A text-figure (Diagram C) is given to 

 illustrate their nature. 



' It is, however, sometimes laterally disposed, and in one or two rare instances lies 

 distinctly on the convex side of curvature. 



