224 



TABULATE CORALS. 



more fully by Mr R. Etheridge, jun., and myself, to be of a 

 most remarkable character. The entire visceral cavity of each 

 polype is open from top to bottom, and we have been unable to 



Fig. 32. — A, A full-grown co\o\\y o{ Motiilopora a-assa, M'Coy, sp., growing upon the stem of 

 a Crinoid, of the natural size. B, A younger colony of the same, encircling a Crinoidal 

 column, viewed from above, of the natural size, c, A detached fragment of the corailum 

 of the same, of the natural size. D, Transverse section of a young colony of the same 

 growing upon a Crinoidal column, enlarged two and a half diameters. (The visceral 

 chambers of the corallites are largely filled with matrix, and the peculiar reticulated tissue 

 of the skeleton is here and there visible in the wall, while the whole has been finally en- 

 veloped by the growth of the stem of the Crinoid.) E, Longitudinal section of a single 

 corallite of the same, enlarged five diameters, showing the open visceral chamber, the 

 fibrous wall, and the reticulated structure of the wall of the calice. F, A portion of the 

 reticulated tissue still further enlarged. Carboniferous Limestone of Lancashire (British 

 Museum.) 



detect any traces of tabulae (fig. 32, d and e). The wall of the 

 theca is exceedingly thick, and throughout the greater part of 

 its extent it seems to consist wholly of delicate concentric layers 

 of sclerenchyma firmly united with one another. In parts of 

 the corallite, however, and especially as the calice is approached, 

 the concentric lamellae of the wall become separated from one 

 another, so as to include a series of distinct interspaces or 

 cavities, which are approximately parallel to the axis of the 

 visceral chamber, diverging slightly outwards, and which are 



