STROMATOPORA HUPSCHII. 177 



surface (Plato XXII, fig. 6) exhibits coarse vermiculate ridges, which inosculate 

 with one another so as to form a network corresponding with the reticulated 

 skeleton, while the elongated or rounded meshes correspond with the apertures 

 of the zooidal tubes. The surface also shows numerous astrorhizjfi of a 

 characteristic ramified type, which vary in size and distance, but usually have 

 their centres about a centimetre apart. 



As regards internal structure, the skeleton-fibre (Fig. 20, a and b) is coarsely 

 porous, and is unusually stout (about j mm. in diameter, or rather more). The 

 ccenosteal tissue is of the completely " reticulate " type, the radial pillars and the 

 trabecules of the " concentric lamina? " being fused into a continuous network. 

 Vertical sections (Plate XXII, fig. 3), however, show that the radial pillars exist 

 as distinct structures, united at irregular intervals by horizontal or oblique 

 connecting-processes, and separated from one another by very well-developed zooidal 



Fig. 20. 



:.■ 



A I 



C D ' ■ u 



Fig. 20. — A. Tangential section of Stromatopora Supschii, enlarged twelve times, showing the 

 reticulate skeleton and the porous skeleton-fibre. B. Vertical section of the same, 

 similarly enlarged, showing the tabulate zooidal tubes. C and D. Tangential and vertical 

 sections of Stromatopora Biicheliensis, similarly enlarged. Middle Devonian. 



tubes (Fig. 20, b), which are intersected by occasional remote tabulae. About five 

 radial pillars, with their intervening zooidal tubes, occupy the space of two milli- 

 metres measured transversely. Tangential sections (Plate XXII, fig. 4, and 

 woodcut, Fig. 20, a) show the loosely-woven and coarse netwoi'k of the reticulated 



