A CARBONIFEROUS FAUNA FROM NOWAJA SEMLJA. 155 



on the whole the separation of the hexameral species seems advisable. Many of the 

 latter are of considerable size, and certainly cannot be regarded as early stages of the 

 multi-septate forms. 



These peculiar genera are difficult to classify. They differ from ordinary Palaeozoic 

 corals in at least two important respects. In the first case, certain species apparently 

 have no epitheca, for the dark median line of the septa passes completely through the wall 

 to the exterior, instead of being interrupted by an epitheca. In the second case, in 

 certain species a protoseptal stage with four septa at right angles to one another seems 

 to be indicated, and such an arrangement is at variance with our knowledge of other 

 Anthozoa. The remarkable external ornamentation of such species as Hexaphyllia 

 mirabilis, and the general habit of growth, are also peculiar. 



Further investigation of these curious genera is certainly needed before their 

 systematic position can be secured. 



Hexaphyllia m'coyi (Duncan). (PL I. fig. 9.) 



Heterophyllia m'coyi, Duncan, Phil. Trans., clvii. p. 645, pi. xxxi. figs. 3a, 3c. 



Heterophyllia m'coyi, Thomson, "Corals Curb. Syst. Scotland," Proc. Phil. Soc. Glasgoiv, 1883, p. 118, 

 pi. x. figs. 20, 20a. 



There are several fragments of this species, varying from 2 to 6 mm. in diameter. 



The corallurn has a smooth exterior and is six-sided, with parallel walls. There is a 

 low ridge at each angle, to which one of the six septa extends. The dark median line 

 of each septum passes through the wall (which is very thick) to the exterior, and in 

 weathering out gives rise to a faint longitudinal groove down the middle of each of the 

 external ridges (" costae " of Duncan). No complete specimens have yet been recorded ; 

 the whole corallurn may have been 20 cm. or more in length, tapering with extreme 

 slowness. 



In transverse sections of mature examples the septa are rather thick, and have a 

 regular hexameral disposition. In young specimens they are cruciform, one arm of the 

 cross being forked at each end ; while six septa are therefore still present, it appears 

 possible that in still younger stages there may be only four, arranged at right angles 

 to one another. 



The tabula; are very close together ; they are bent sharply downwards near the wall, 

 and upwards in the centre, but are almost flat in the middle. The appearance of a 

 vertical section varies according to its distance from the centre of the coral. If the 

 section be cut close to the wall, the tabulae appear very steeply inclined upwards, but 

 when cut down the centre of the coral they are more flattened (see PL I. fig. 9). 



Remarks. — Neither Duncan nor Thomson figures any vertical section of this species, 

 the former simply remarking that " the endotheca [ = tabulae] is very abundant." 



The type was not available for examination, but another specimen, in every way 

 identical with that figured by Duncan, and procured from a similar horizon in Ayrshire, 

 is in the collection of Mr James Neilson of Glasgow. Mr Neilson very kindly allowed 



