178 BRITISH STROMATOPOROIDS. 



skeleton, in which no traces of the radial pillars (as distinct structures) are recog- 

 nisable. The apertures in this network correspond with the zooidal tubes, and 

 some of these are simply circular, while others are confluent, and thus give rise to 

 elongated and sinuous meshes. 



Obs. — The general form of the ccenosteum in this species is that of a thick 

 lamina or cake, with an inferior epithecal membrane. Some examples, however, 

 are massive in growth and irregular in form, and may not have possessed an 

 epitheca. The upper surface is devoid of elevations, though it is probable that 

 pointed prominences or " mamelons " corresponding with the astrorhizae were 

 present in the variety of the species which I shall term S. Hiipschii, var. seposita. 

 Latilaminar growth is not clearly recognisable, as a rule, and the general skeletal 

 structure is very characteristic. The skeleton-fibre (Fig. 20, a) is coarsely porous, 

 and is unusually thick, the general ccenosteal reticulation being loose, with 

 usually elongated and sinuous meshes. The zooidal tubes, as seen in vertical 

 sections (Fig. 20, b), are very clearly developed, but they show comparatively few 

 tabulas, or they may be even devoid of these structures. 



Astrorhizas (Plate XXII, fig. 5) are very abundantly developed, but are usually 

 of small size, while they melt away rapidly at their circumference into the general 

 reticulated tissue of the skeleton. In that form of the species which I propose to 

 call 8. Hiipschii, var. seposita, the astrorhizas are superimposed in regular vertical 

 systems, which are surrounded by concentrically disposed lamina?, penetrated 

 more or less transversely by the radial pillars, thus giving rise to regular 

 "astrorhizal cylinders." The spaces between these cylinders may be simply filled 

 by loose reticulated tissue of the type ordinarily characteristic of this species, or 

 may be occupied by undulated laminae in a manner similar to what occurs in 

 Actinostroma verrucosum, G-oldf. sp. (figured in Plate XVI, fig. 1). It is probable 

 that in this variety of 8. Hiipschii each astrorhizal cylinder would project above 

 the upper surface of the coenosteum as a pointed " mamelon ;" but none of my 

 examples exhibit the general form or exterior. In its minute structure 8. 

 Hiipschii, var. seposita shows nothing to distinguish it from the normal form 

 of the species. 



Stromatopora Hiipschii very commonly occurs in the " Caunopora-state." It 

 is, indeed, comparatively rare to meet with an example of this species which is 

 not penetrated by " Caunopora-tubes." Such tubes vary considerably in size in 

 different examples, but they can be commonly shown to possess funnel-shaped 

 tabula; in their interior (Plate X, fig. 9), and they sometimes possess radiating 

 septal spines in addition. In some specimens, the " Caunopora-tubes " are short, 

 and give off numerous lateral stolons, reminding one of an Aulopora-colonj. In 

 other cases, the tubes are straight, regularly parallel, and continuous throughout 

 considerable vertical distances, thus reminding one rather of a S/jriiigopora-colonj. 



