imperfectly -hnown Species of Stromaioporoich. 235 



and is furnished with a striated epitheca, but which is some- 

 times encrusting. The surface is covered with minute 

 rounded tubercles, many of which, in well-preserved examples, 

 are seen to terminate in minute circular apertures (zooidal 

 pores). The surface is without marked eminences or "marae- 

 lons ;" and though astrorhiza3 are often present they are very 

 irregularly distributed, and are apparently sometimes wanting. 

 The astrorhizal canals may be furnished with " astrorhizal 

 tabulfe," which have sometimes a vesicular character (PL VII. 

 fig. 9) . The skeleton-fibre is thick and minutely porous or 

 tubulated ; the radial pillars are distinct, and often to some 

 extent " continuous." Hence, in tangential sections, the 

 cut ends of the pillars are largely visible as distinct structures. 

 The " concentric laminae " are well developed and are placed 

 from i to -^ millim. apart, as also are the radial pillars. 

 Zooidal tubes are irregularly developed, being usually numerous 

 and generally intersected by a variable number of tabulfB. 



Ohs. I have elsewhere given the reasons which have induced 

 me to reject the generic name of Diapora, proposed by Bar- 

 gatzky, for this species. The " Caunopora- tubes," which 

 constituted an essential feature in Bargatzky's genus Diapora^ 

 are very commonly present in this species, but are likewise 

 often wanting ; while in other closely allied species they seem 

 to be always absent. [In one of the specimens here figured 

 these " Caunopora-tubes " are developed, but in the other 

 they do not exist at all.] Apart from minute details, 8. lami- 

 nata is distinguished from its nearest allies [S. eifeliensis^ 

 Nich., and 8. granuJata^ Nich.) by the much more extensive 

 development of the zooidal tubes, aiid the more complete 

 structure of the radial pillars than is the case in these latter. 



Formation and Locality. Abundant in the Middle Devo- 

 nian of Biichel (Paffrath district) . 



8tromatoporella eifeliensis, Nich. 

 (PI. VIII. figs. 5, 6, 7.) 



The coenosteum in this species is laminar and expanded, 

 sometimes with a basal epitheca, but more commonly attached 

 by the whole of the lower surface to some foreign body, and 

 varying in thickness from a couple of millim. up to 5 or 6 



whicli the fusion of the radial and concentric elements of the skeleton 

 into a reticulate framework is much less complete. The radial pillars 

 and concentric laminae remain quite recognizable, and tangential sections 

 show more or less largely the cut ends of the radial pillars, instead of 

 exhibiting a vermiculate reticulation. The zooidal tubes are much less 

 highly developed in most species of StromntoporeUa than they are in 

 8tromatoi)ora, and they usually only extend from one iuterlaminar space 

 to the next above. 



