40 Mlt. J. A. DOUGLAS ON GEOLOGICAL SECTIONS [vol. lxxvi, 



Cyathaxonia sp. (PI. I, figs. 4 ft & 4 b.) 



Description. — Corallum simple, conical, slightly cornute. Epitheca 

 strongly costate. Eighteen major septa, radially disposed, and of more or less 

 equal length ; slightly swollen at their inner extremities. These alternate 

 with a series of minor septa, two of which (the fourth from the cardinal 

 .septum on each side) are more pronounced than the others. 



The centre of the corallum is occupied by a rod-like columella, oval in cross- 

 section, which appears to be a structure independent of the septa. In the 

 earlier stages of growth the ends of the major septa are fused to it, and at 

 first sight seem to take part in its construction. In some cases, however, the 

 ■central core has been dissolved away, leaving a hollow tube, and thereby dis- 

 closing its true character. In the mature stages the counter-septum alone 

 remains attached, its continuation through the solid axis being disproved by 

 the absence of any trace of a mesial line. 



The structure of the columella, therefore, is distinctly Cyathaxonid in cha- 

 racter, for it has clearly not been formed, as in the Lophophylla, by the upward 

 growth and thickening of the counter-septum. A fossular break is merely 

 indicated by a shortened cardinal septum. No trace of tabular intersections 

 were observed. 



Affinities. — The Cyathaxonid type of columella, the presence of minor 

 septa, and the apparent lack of tabulse, readily distinguish this form from any 

 of the preceding. The solidity of the central axis, and the strongly-costate 

 epitheca, suggest that it is closely related to Gyafhaxonia costata M'Coy, the 

 relationship of which with the Densiphylloid Zaphrentes has already been 

 noted by Vaughan. 1 In the earlier stages of its growth it shows a certain 

 resemblance to Carcinophyllum simplex Garwood, 2 but differs from that form 

 in its small size, less number of major septa, and the absence of any peripheral 

 •dissepimental zone. 



Zaphrentis aff. enniskilleni Edwards & Haime. (PL I, figs. 6 a & 6 5.) 

 Description. — Corallum conical, cornute. Epitheca smooth, with annular 

 striations. Cardinal fossula deep, extending to the centre of the corallum ; 

 situated on the concave side ; narrow, and with almost parallel sides ; widening 

 slightly towards the wall, the expansion becoming more pronounced in 

 sections near the calyx. Position of alar fossuke clearly defined by a septal 

 break and discontinuity of tabular intersections. Major septa, 35 in adult, 

 strongly thickened, especially in the anti-fossular group ; their inner ends are 

 coalescent in the younger stages of growth. Cardinal septum very short. 

 Curvature of the septa convex to the cardinal fossula, ill-defined in youth but 

 becoming pronounced in the adult. Minor septa absent or undeveloped. 

 Tabulae few in number and evenly spaced. 



Affinities. — This form appears to be a typical representative of the 

 ' Enniskilleni ' gens, differing from the type chiefly in the absence of minor 

 septa. In the character of the fossula, the number and disposition of the 

 septa, and the thickening of the counter-septum, it most nearly approaches 

 the form figured by Vaughan from the Posidonomya Beds of Loughshinny. 3 



The limestone of the Viscachani district, as has heen mentioned 

 above, is divisible into an upper grey cherty limestone and a lower 

 purple limestone, the latter being largely composed of fragmentary 

 •crinoid -remains. With the exception of Zaphrentis aif. ennis- 

 killeni and Productus aff. cora, all the forms mentioned in the 

 faunal list on p. 41 appear to be restricted to the lower beds ; and, 

 since the lithological change is also accompanied by a slight 

 discordance in the dip, it is possible that a gap in the sequence 



1 Q. J. G. S. vol. lxii (1906) p. 318. 



2 Ibid. vol. lxviii (1912) p. 556 & pi. xlviii, figs. 3a-3c. 



3 Ibid. vol. lxiv (1908) pi. xlix, fig. 13. 



