STROMATOPORELLA CURIOSA. 213 



presence of " mamelons." There is no other species of Stromatoporella which 

 8. solitaria resembles with such closeness in internal structure as to demand a 

 detailed comparison. 



Distribution. — 8. solitaria is not uncommon in the Middle Devonian Lime- 

 stones of the Auberg, at Gerolstein in the Eifel. It is very difficult to identify 

 this form among the species of Stroynatoporella which occur in the pebbles of 

 Devonian Limestone in the Triassic conglomerates of Devonshire, since such de- 

 rived specimens necessarily exhibit no surface-characters. I am disposed, how- 

 ever, to think that the sections figured by me in Plate II, figs. 9 and 10, and 

 doubtfully referred to S. eifeliensis, really belong to the present species. 



7. Stromatoporella curiosa, Barg. sp. PI. XXVIII, figs. 1 — 3. 



Stromatopoea polymoepha, Goldfuss. Petref. Germ., pi. lxiv, figs. 8 a, 8 c, and 



8d (cset. excl.), 1826. 

 — curiosa, Bargatzky . Die Stroinatoporen des Rheinischen Devons, 



p. 55, 1881. 

 Steomatoporella curiosa, Nicholson. Ann. and Mag. Nat. Hist., ser. v, 



vol. xviii, p. 8, pi. i, figs. 1—3, 1886. 



Ccenosteum incrusting, thin, attached by the whole of the inferior surface to 

 some foreign body, and usually developing externally numerous irregular pointed 

 eminences, at the extremities of which the astrorhizge open. Surface usually 

 covered with minute rounded tubercles, the apices of which may be perforated, 

 and also exhibiting branched astrorhizal canals ; in other cases part or the whole 

 of the surface may be covered by a thin calcareous membrane, which exhibits 

 few or no apertures of any kind. As regards internal structure, the skeleton-fibre 

 is minutely porous, and the skeletal tissue is of the imperfectly reticulate type. 

 The concentric lamina? are thick and well marked, often with a median clear line in 

 each (as seen in vertical section), and they are placed from j to ^ millimetre apart. 

 The transversely divided ends of the radial pillars can be more or less extensively 

 recognised as distinct structures in tangential sections. The astrorhizas are fur- 

 nished with vertical axial canals, and astrorhizal tabuke may be sparingly present. 

 Definite zooidal tubes are not recognisable. 



Obs. — This is a typical example of an incrusting and parasitic Stromatoporoid. 

 It envelops Rugose Corals or other organisms, and forms crusts varying in thick- 

 ness from less than a millimetre up to 5 or 6 millimetres One of its most charac- 

 teristic and conspicuous external features is the fact that the exterior is more or less 

 extensively covered with pointed conical eminences (Plate XXVIII, fig. 1), which 

 may be imperforate, or which may terminate in an aperture corresponding with 



