302 TABULATE CORALS. 



tubes, and especially aggregated in the central depressed areas 

 of the monticules, and in the star-like prolongations which run 

 out from these ; their walls thin and apparently often wanting. 

 Large corallites with few remote tabulae ; small corallites with 

 very numerous close-set tabulae, which often anastomose with 

 those of neighbouring tubes. 



Obs. — Passing over the obvious and well - known external 

 features of the corallum in Constellaria antJieloidea, I may 

 make a few remarks upon the appearances presented by thin 

 sections. Tangential sections (PI. XIV., fig. 5 a) present some 

 peculiar difficulties of preparation, owing to the irregularity of 

 the surface due to the monticules, but when properly made, 

 they are very instructive. They exhibit both sets of corallites, 

 the larger being conspicuous both by their size and their cir- 

 cular or oval form, and by the fact that each is bounded by a 

 thick and apparently double wall. It is only in the stellate 

 ridges of the monticules that the large corallites are at all ex- 

 tensively in contact ; but in the intervals between the monti- 

 cules they are only partially contiguous, and are separated 

 by more or less extensive interspaces. These interspaces, as 

 well as the central areas of the monticules and the branching 

 diverticula therefrom, are occupied by the smaller corallites. 

 The appearances presented by these vary under different cir- 

 cumstances, and in different parts of the section ; and I am not 

 at present able to explain some of the appearances which they 

 exhibit. They are best studied in the central depressed areas 

 of the monticules, and in their most perfect condition they are 

 seen to be angular in shape, and to be bounded by thin and 

 delicate walls, which, however, are often partially imperfect, 

 thus allowing neighbouring tubes to communicate. In other 

 cases, the divisional walls between the small corallites seem 

 wholly wanting, and the central areas of the monticules exhibit 

 simply minute rounded and remote pores, together with other 

 peculiarities which I must leave for future examination. In 

 the interspaces between the large tubes, also, the smaller tubes 

 only rarely seem to possess complete bounding walls, and here, 



