64 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [JuilC 14, 



generally numerous ; intermediate spaces opake-white ; pores very 

 minute ; fibrous structure microscopic, meshes irregular, fibres more 

 or less curved^ variable in character. 



The largest specimen (fig. 1) submitted to examination was irre- 

 gular in form ; its extreme length was rather more than seven lines, 

 breadth six lines, and thickness or height three and a half lines. It 

 had been attached when living to an unequal surface by a thin layer, 

 which extended beyond the base of the united ridges. The nature 

 of this lamina was not clearly detectable, but it appeared to be inti- 

 mately connected with the spongeous structure which sometimes ex- 

 tended over it, and in one part to have a striped surface with lacunae 

 or pits, similar to what was clearly exhibited in an indubitable por- 

 tion of the fossil. The specimens were in general so intimately united 

 to the sandy matrix, that it was almost impossible to obtain mechani- 

 cally a clean, perfect exterior. So far as ascertained, it consisted of 

 opake matter, more or less discoloured, and not a trace was detected 

 of a dense or distinct surface-layer. Fractured portions exhibited an 

 opake-white substance, and translucent spots of calcareous spar, 

 which marked the inward range of the lacunae or channels. Polished 

 sections and transparent slices (fig. 3) displayed a similar general 

 construction. Of the minuter textures some remarks will be found 

 in subsequent paragraphs. 



In the two perfect specimens, as well as in the fragments examined, 

 the ribs or ridges (fig. 1) showed not the slightest approach to the 

 regularity of the Streitberg species, or to a development from a deter- 

 mined centre, but the greatest irregularity in the mode of growth ; 

 and their outline, in place of being uniformly curved, was more or less 

 tuberculated or conical ; and their sides, so far from thickening sym- 

 metrically downwards, were often almost perpendicular, and the in- 

 crease was frequently unequal on opposite sides, or in different por- 

 tions of even the same side. These discrepancies are believed to indi- 

 cate something more than varieties of a species. 



It has been already stated, that the opake matter was not redu- 

 cible, by the powers employed, to distinct spicula, but preserved an 

 apparently granular texture under lenses which exhibited not merely 

 the spicula of Grantice and HalichondricB, but most fully their pecu- 

 liarities of form. That the matter was an original secretion, and not 

 an infiltered calcareous sediment, was inferred from its not filling the 

 immediately adjacent lacunae ; while the calcareous spar, which chiefly 

 occupied those cavities, was unadulterated by the argillaceous or other 

 finer particles of the overlying matrix. The minute particles visible, 

 in greater or less number, in many of the lacunae, and often giving 

 them a cloudy aspect, were similar in nature to those which composed 

 the surrounding dense substance, and were assigned, as well as an 

 occasionally evident diminution in the size of the hollows, to progress- 

 ive secretions dependent upon the changed wants of the living body 

 during its upwards or outwards extension. In colour the matter 

 resembled that of the solid portions of calcareous Anthozoa, and the 

 texture was not very dissimilar from what may be noticed in tertiary 



