202 Br. G. J. Hinde — Western Australian Fossils. 



species of Fistulipora, and also in Eexagonella Icevigata, Waageu and 

 Wentzel (Pal. Indica, ser. 13, pi. 115, fig. 5). 



On the surface of the branches, the cells are arranged in rows 

 which radiate from the maculae as centres. The cells in the rows 

 are somewhat less than half a millimetre from centre to centre, 

 and about the same distance between the rows. The cell-apertures 

 are slightly oblique to the surface, and there is a distinct elevated 

 lip, in some cases semilunate or crescentic in form (Fig. 5c). The 

 cells near the maculae are larger, more oblique, and with thicker 

 lips than others. 



As a rule, the cell-apertures are open, but in many instances the 

 cells are partially or entirely closed by calcareous lids, placed just 

 within the lip of the cell (Fig. 5c). These lids are flat or slightly 

 convex, and usually incomplete, a central or sub-central space 

 remaining open. In other cases this aperture is wholly closed by 

 a minute central papilla. Occasionally the lid is evenly convex, 

 and projects beyond the rim of the cell-wall. These lids appear to 

 be distinct from the tabulae in the lower portion of the cell ; they 

 are thicker ; convex, instead of flat or concave : and they are fre- 

 quently incomplete. 



The spaces between the cells, where they radiate upwards to the 

 surface from the axial lamina, are occupied by interstitial tissue or 

 cancelli ( = mesopores) (Fig. 5b). This is of two kinds ; one, 

 occupying principally the central portion of the branches, is mainly 

 vesicular, and formed by convex vesicles arranged sometimes in 

 linear series, sometimes irregularly overlapping and dovetailing into 

 each other (Fig. 56). The peripheral portions of the branches on the 

 other hand mainly consist of a solid imperforate tissue deposited 

 in thin concentric zones. Occasionally, however, there is a layer of 

 vesicles within the exterior solid zone, and sometimes a thin solid 

 band intercalated in the central vesicular area. The solid substance 

 does not, however, seem to be a mere infilling of the vesicles ; but 

 it is of a distinct character replacing the vesicles. On polished 

 surfaces, and in sections viewed by reflected light, this substance 

 can be seen to consist of delicate rods or spines vertically arranged 

 and imbedded in a lighter material, and it appears that the minute 

 tubercles with which the surface is covered are the upward exten- 

 sions of these bodies. In transparent, transverse sections, this solid 

 tissue has an indistinct cloudy appearance, due to innumerable, 

 opaque dots — the section of the rods — in a lighter substance 

 (Fig. 5d). The thickened portion or lips of the cells likewise 

 consists of these solid spines or rods. 



No mention is made of this solid interstitial tissue in the Punjab 

 species of Rexagonella, but it is shown in the figures of H. ramosa 

 (Pal. Indica, ser. 13, pi. 107, fig. 3c). Similar tissue is likewise 

 present in certain specimens of Fistulipora incmstans, which have 

 been described by Mr. John Young, F.G.S. (Ann. & Mag. Nat. Hist. 

 April, 1888, p. 245), and in Goniocladia cellulifera, E. Eth., jun. 

 (Geol. Mag. Dec. I. Vol. X. p. 433, PI. XV.) 



The general question as to the relation of Eexagonella or Fistulipora 

 to Polyzoa or Corals is too wide to be properly discussed here ; but 



