Fistulipora incrustans, Phill. (F. minor, M^Coy). 245 



very much the same character as those seen in the autopores 

 and mesopores of Heteropora neozelanica^ Busk, which are 

 figured and described by Prof. Nicholson in his ' Monticuli- 

 pora,' p. 69, fig. 9 (1881). In the Carboniferous form, how- 

 ever, the spines are only seen in the autopores, and in this 

 respect it differs from the species of Heteropora above noted, 

 where they are found in both groups of cells. The spines 

 appear to be as slender and as numerous as those of H. neo- 

 zelamca^ there being from ten to twelve in many of the 

 sections, in which they are seen to be arranged within the 

 circle of the cells at slightly varying distances from one 

 another. They also vary in their length within the tubes, 

 as in Heteropora^ and many of them have become thickened 

 by a secondary deposit of calcite that now renders them more 

 conspicuous in the sections. I find them most numerous and 

 best preserved in those portions of the tubes that lie at a little 

 distance below the outer surface of the zoarium. In the 

 younger stage of the autopores the spines are seen to be rare 

 or absent. Tlie tabulaj in the tubes are moderately common, 

 and in those portions where the spines exist the latter are 

 seen amongst the tabulae projecting inwards from the cell- 

 walls, but apparently in no regular order of arrangement. 

 The species of Fistulipora under notice has the outer surface 

 of the zoarium often well preserved. On it the mouths of the 

 autopores are seen to be nearly circular in form, having a 

 slightly raised lip or rim all round the cell. The interspaces 

 between the autopores that are occupied by the mesopores 

 show in most specimens a thick sclerenchyma-layer at the 

 surface that completely conceals the mesopores. This layer 

 also covers the mesopores that lie deeper within the branches, 

 and in certain stages it forms thick zonal layers all round the 

 stem that separate the mesopores in their layers from each 

 other by the whole thickness of the sclerenchyma-deposit. 



All over the surface of the sclerenchyma-layer, as well as 

 upon the raised lips of the cells, there exist numerous, small, 

 slightly raised tubercles, that give this surface a minutely 

 granulated appearance. Their structure under tlie microscope 

 is seen to be identical with the smaller forms of spiniform 

 tubercles (acanthopores) found in many species of the Monti- 

 culiporidte. In this species of Fistulipora^ however, they 

 seem to be much more numerous than I have yet seen noted 

 in any other member of the genus. One other interesting 

 character of this organism, as illustrated by tangential sections 

 of the branches when cut below their surface, is the occur- 

 rence of similar acanthopores in the thicker inferior layers of 

 scleienchyma that 1 formerly mentioned as forming the zonal 



