AULOPORID^E. 223 



6, 1872), and this accurate observer states that the visceral 

 chambers of the corallites are entirely hollow, and that they 

 communicate freely with one another by their bases. This 

 latter point is doubtless correct ; but Mr R. Etheridge, jun., 

 and myself have made thin sections of specimens from the 

 Carboniferous of Scotland which we are unable to distinguish 



o 



from C. Michelini, E. and H., and we find that in these the 

 visceral cavities of the corallites are intersected by a few 

 remote, delicate, complete tabular, which are either straight or 

 slightly curved (fig. 31, c). It would appear, then, that so far 

 as at present known there is nothing in the internal structure 

 of Cladockonus, M'Coy (^ Pyrgia^ Edw. and H.), which would 

 separate it from Aulopora, Goldf., and the generic distinctness 

 of the two can only rest upon the feature that the corallum of 

 the former is erect, whereas in the latter it is creeping and 

 parasitic. So far as known, the species of Cladochonus appear 

 to be exclusively Carboniferous. 



Lastly, it remains to say a few words upon the singular 

 genus Monilopora, Nich. and Eth. jun., which includes only 

 the curious M. (Cladochonus] crassa, M'Coy, sp., of the Carbon- 

 iferous rocks. In this singular form the corallum (fig. 32, A) is 

 decidedly "Auloporoid" in its general appearance, consisting of 

 a creeping tubular basis, which at intervals throws up curved 

 conical corallites, which are of much larger size than is usual in 

 Aulopora, and are free throughout the whole or the greater part 

 of their height. As a rule, the corallum commences in the form 

 of a ring of such corallites, with their connecting basal stolons, 

 encircling the column of a Crinoid like a necklace ; and by the 

 continued growth of the latter the colony often becomes entirely 

 buried within the stem of the Crinoid, only the calices appear- 

 ing on the surface. Adult examples, again, often lose a good 

 deal of this ring-like arrangement, and present themselves as a 

 confused aggregation of corallites quite resembling a magni- 

 fied Aulopora. The minute structure of Monilopora, as eluci- 

 dated by means of thin sections, has been shown by Mr 

 Rofe (Geol. Mag., vol. vi. p. 352, 1869), and subsequently 



