Hydractinia, Parkeria, and Stromatopora. 67 



it sliced and polished, has kindly submitted for my examina- 

 tion. 



Whether the tissue-fibre of this fossil was calcareous or not, 

 I am unable to decide, further than that, if right in identifying 

 the " branched, tortuous, dendriform fibre " on the surface of 

 the fossil with the coenosarcal stolon-tubulation of Hydractinia 

 ecMnatay the former also may have undergone the same 

 change — that is, from chitine to carbonate of lime. 



I have stated that there are boss-like projections irregularly 

 scattered over the surface of Loftiisia persica^ corresponding 

 with a wavy condition of the spiral lamina opposite them in 

 the section, and that they also bear branched lines running 

 over their summits respectively, which look like traces of the 

 stellate systems seen in Bradya and Stromatopora (tig. 18, c) ; 

 but I have also added that most of these appear to be acci- 

 dental. How far the reason I have assigned for this may be 

 accepted, remains for future observation to determine. 



It might be said that Bradya tergestina is a Stromatopora ; 

 but if so, Stromatopora is handed down to us in Parheria ; for 

 the tissue-fibre and radiating tubes in Parheria are, in a tan- 

 gential section, identical with those both of Bradya and Stro- 

 matopora. 



I regret that the fossil reached me after my plate of illus- 

 trations to this paper had been filled up ; but a diagram of the 

 tissue-fibre would only be a repetition of that which is given 

 of Parheria in fig. 14, minus the incrustation ; and an almost 

 facsimile of the stellates may be seen in fig. 19, making 

 allowance /or the larger size and lesser number of bosses in 

 Bradya tergestina'^ while the branched fibre in prominent 

 relief on the surface is represented in the coenosarcal tubula- 

 tion of Hydractinia ecMnata (fig. 3) . 



D'Orbigny gives a figure, viz. Stellispongia variabilis^ 

 very much in appearance like the above fossil, which is stated 

 to extend from the Trias (Saliferien) to the Eocene (Suesso- 

 nien) strata inclusively (Cours Element, de Pal^ont. et d. Geo- 

 logic, t. i. p. 214, fig. 338). 



Stromatopora. 



My friend Mr. W. J. Sollas, who has for some time past 

 been directing his attention to the different species of Stroma- 

 topora within his reach, and who has generously presented me 

 with some specimens, and brought to mj notice others, had, 

 from the regular hexactinellid structure of one in particular (to 

 which I shall return hereafter), been, like myself, inclined to 

 the idea that it was originally a Sponge. But when I learned 



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