GENERA OF CH&TETIDM AND MONTICULIPORID^E. 303 



as in the monticules, there is the curious feature that the cavi- 

 ties of the smaller corallites seem to be very commonly obliter- 

 ated by a secondary deposit of light-coloured sclerenchyma. 

 Vertical sections (PI. XIV., fig. 5 b) render it certain, however, 

 that whether or not their walls are developed in a complete 

 form, the interspaces between the larger tubes and the central 

 areas of the monticules are alike uniformly occupied by the 

 smaller corallites. In sections of this kind, we see that the 

 large corallites exclusively occupy the central part of the cor- 

 allum, in which region they are thin-walled, and possess few or 

 sometimes no tabulae. As they bend outwards, in approaching 

 the surface, their walls become thicker, and the tabulae, though 

 still very few and widely remote, become somewhat more nu- 

 merous. The small corallites are only developed in the inter- 

 spaces between the larger tubes in the outer portion of the 

 course of the latter, so that they occupy only a superficial zone 

 of the corallum ; and they are at once recognised not only by 

 their small size, but also by their very numerous and close-set 

 tabulae. Sections of this kind further demonstrate that the 

 walls of the smaller tubes are really often wanting, though at 

 other times clearly recognisable ; their tabulae, in the former 

 case, becoming laterally coalescent and often more or less ex- 

 tensively vesicular. This latter feature is particularly observe 

 able in the aggregations of the smaller corallites which consti- 

 tute the central depressed areas of the monticules. 



The affinities of Constellaria seem to be clearly with Fis~ 

 tulipora, M'Coy, in which, likewise, the bounding- walls of the 

 smaller tubes may in some forms become so far obsolete as to 

 allow of the tabulae assuming a completely vesicular structure. 

 The sub-genus is, however, sufficiently separated from Fistuli- 

 pora by the much less complete development of the small tubes, 

 which in the latter type always completely encircle and isolate 

 the larger tubes ; while the star-shaped form of the monticules 

 is another well-marked distinguishing character. 



Formation and Locality. Rare in the Cincinnati group, 

 Cincinnati, Ohio. 



