GENERA OF CH^TETID^. AND MONTICULIPORID^E. 311 



Obs. This beautiful species, in the essential features of its 

 organisation, is clearly nearly allied to the two forms previously 

 described, and especially to F. incrassata. It agrees more 

 particularly with this last in the comparatively large size and 

 markedly angular form of the interstitial corallites, and in the 

 fact that there is but one single series of these separating the 

 round tubes. In both species also the surface exhibits, alone 

 or principally, the projecting apertures of the round corallites 

 (PI. XV., figs. 2 and 2 a), the mouths of the angular intersti- 

 tial tubes seeming to be often closed by a thin calcareous mem- 

 brane. The form of the corallum, however, is in the present 

 species always that of a thin, often contorted expansion, the 

 under surface of which is clothed by a striated and plicated 



Fig. 41. Fistulipora proporoides, Nich. A, Part of a vertical section, enlarged twenty times, 

 showing the different tabulation of the two sets of corallites. B, Part of a tangential 

 section, showing the round and the angular corallites, enlarged twenty times : a, a, Round 

 or "large" corallites ; b, b, Angular or " small " corallites. 



epitheca ; the round corallites are strictly round or oval, and 

 are not contracted at one point ; the " maculae " are sometimes 

 obsolete ; and there is the striking internal difference that the 

 angular interstitial corallites are always limited by complete 

 walls, and are intersected by numerous horizontal tabulae, which 

 never assume a vesicular character (Fig. 41, A). This last- 

 mentioned feature, among other points of distinction, sufficiently 



