Prof. H. A. Nicholson on some neic or 



III. — On some neio or imperfectJy-kyiown Species of 

 Stroma fopor Olds. By H. Alleyne Nicholson, M.D., 

 D.Sc, Eegius Professor of Natural History in the Uni- 

 versity of Aberdeen. — Part II. 



[Plates I. & II.] 



StromatoporeUa cnriosa^ Barg., sp. 

 (PI. I. figs. 1-3.) 



Stromatopora polymorpha^ Goldfuss, Petref. Germ. pi. Ixiv. figs. 8 a, 8 c, 



&8d (ciBt. excl.) (1826). 

 Stromatopora ciinosa, Bargatzky, Die Stromatoporen cles rheiiiisclien 



r)evons,p. 55 (1881). 

 ? Stromahporu nvlliporoules, Nicholson, Report on the Paleontology of 



the Province of Ontario, p. 78 (1875). 

 P Ccc7iostroma incrustans, Hall & Whitfield, Twenty-third Annual Ee- 



port on the State Cabinet, p. 227, pi. ix. tig. 3 (1873). 



Coenosteum encrusting, thin, attached by the whole of the 

 inferior surface to some foreign body, and usually developing 

 externally numerous irregular pointed eminences, at the ex- 

 tremities of which the astrorhizse 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 ^qw or 

 no a])ertures 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 laminjB are 

 thick and well-marked, often with a median clear line in each 

 (as seen in vertical section), and they are placed from I to 

 i millim. apart. The transversely divided ends of the radial 

 pillars can be more or less extensively recognized as distinct 

 structures in tangential sections. The astrorhizas are fur- 

 nished with vertical axial canals, and astrorhizal tabula? may 

 be sparingly present. Definite zooidal tubes are not recog- 

 nizable. 



Ohs. This is a typical example of an encrusting and para- 

 sitic Stromatoporoid. It envelops Pugose corals or other 

 organisms, and forms crusts varying in thickness from less than 

 a millimetre up to 5 or 6 millim. One of its most character- 

 istic and conspicuous external features is the fact that the 

 exterior is more or less extensively covered with pointed coni- 

 cal eminences (PI. I. fig. 1), which may be imperforate, or 

 which may terminate in an aperture corresponding with the 

 centre of one of the astrorhizal systems. These eminences or 

 *' mamclons " may be comparatively large, sometimes more 



