On the Germs Cladochonus. 295 



microscopical sections of M. crassa have entirely confirmed Mr. 

 Eofe's discovery of this reticulated tissue, but have failed to 

 demonstrate its existence elsewhere than in the substance of the 

 walls of the corallites. So far as our observations go, we find the 

 visceral chamber of the corallites of M. crassa to be entirely open 

 and free from tabulae, being usually filled with matrix from end to 

 end (Fig. 2e). This being the case, M. crassa clearly conforms to 

 the definition of the Zoaniharia tubulosa laid down by Milne- 

 Edwards and Haime, and cannot be regarded as a member of the 

 old group of the " Tabulata" In this respect, also, it differs from 

 C. Michelini, as well as from those examples of Aulopora, which we 

 have been able to examine by means of thin sections. Moreover, 

 its structure is quite peculiar, and so far as we toow, such as does 

 not occur in any known coral except the present. The wall (Fig. 

 2e) is extremely thick, and for the most part exhibits a distinctly 

 fibrillated structure, as if composed of successive concentric layers, 

 this structure being equally conspicuous in longitudinal and trans- 

 verse sections. In parts of the corallum, however, the concentric 

 lamella? of the wall become separated from one another so as to 

 include a series of distinct interspaces or cavities, which are ap- 

 proximately parallel to the axis of the visceral chamber, and which 

 are crossed at right angles by numerous delicate cross-bars or 

 trabecular of sclerenchyma (Fig. 2, e and /). This singular 

 reticulate or cellular tissue seems to be sometimes partially developed 

 in the basal portions of the corallum (see Fig. 2, d), but is essenti- 

 ally and principally, if not altogether, present in that portion of 

 the wall which forms the actual cup of each corallite. As before 

 said, we have entirely failed to discover any traces of this cellular 

 tissue as encroaching upon the true visceral chamber ; and there 

 thus arises a discrepancy between our observations and those made 

 by Mr. Rofe (loc. cit.). This, however, may admit of explanation 

 if we suppose that the longitudinal section figured by Mr. Eofe has 

 really been excentric, and that instead of passing along the axis of 

 the visceral chamber, it has really traversed the thickness of the 

 wall. We are at present unable to parallel the peculiar structure 

 of C. crassus, as above described, with that of any other coral known 

 to us, nor can we offer any opinion as to the precise functions or 

 homologies of the cellular tissue of the calicine walls. 



Loc. and Horizon. — Carboniferous Limestone of Derbyshire and 

 Lancashire ; Gilbertson and Eofe Collections, British Museum. 



So far, therefore, as our preliminary examination of certain species 

 of Cladochonus has gone, it would appear that the genus as originally 

 constituted contained corals of very different structure, judging by 

 the conformation of C. Michelini, and C. crassus. The latter has a 

 special structure of its own, quite distinct from C. Michelini, as 

 well as from Aulopora, and for it we have ventured to propose the 

 generic name Monilopora. 



In conclusion, we have to express our thanks to Professor Geikie, 

 F.E.S., for the use of specimens contained in the Collection of the 

 Geological Survey of Scotland. 



