432 Mr. H. J. Carter on the so-called 



Here the matter rested, so far as I myself was concerned, 

 although Prof. Zittel had afterwards to embody the whole of 

 his results in the article " Spongise " of his ' Handbuch der 

 Palaontologie " (2te Lieferung, p. 128 etseq., 1878), of which 

 he kindly sent me a copy ; and had I not unexpectedly come 

 upon the " parcel " of Coral-Rag fossils above mentioned, I 

 probably, on account of other engagements, should not have 

 returned to the subject — although, on account of sundry objec- 

 tions made at the time, I could never heartily accept Prof. 

 Zittel's views of the nature of these sponges ; but finding those 

 in the parcel awoke in me a desire to make myself more par- 

 ticularly acquainted with the Farringdon sponges than I had 

 hitherto been, partly because I could not reconcile myself to 

 the name " Calcispongias " for them, and especially because I 

 had, through the kindness of Mr. Sollas, made myself almost as 

 familiar with Pharetrospongia Strahani as himself previous to 

 the publication of his excellent description and illustrations of it 

 (Quart. Journ. Geol. Soc. May 1877, vol. xxxiii.p. 242, pi. xi.), 

 in which he rightly insists, according to my views, on the 

 originally siliceous nature of this, now calcareous, fossil and 

 so-called " Farringdon sponge." 



At first these fossil sponges appeared to me very much like 

 what Clathrina, Gvay } = Ascetta clathrus, Hackel (which 

 abounds on the rocks here) , would be if fossilized ; but the fact 

 of the Farringdon ones representing in a solid state the fibre 

 of the sponge, and the apparent fibre of Clathrina consisting 

 of a reticulated anastomosing hollow tube representing the 

 excretory canal-system minus the parenchyma which fills up 

 the interstices in other sponges, at once pointed out the de- 

 lusion. 



Hence it becomes desirable to premise that the fibre of the 

 so-called " Farringdon (Coral-Rag) sponges " is entirely 

 composed of calcareous material, solid, white, round, reticu- 

 lated, massive, but still in this massive reticulation assuming 

 a variety of definite forms in which the fibre itself is generally 

 covered with a thin layer of granular crystalline calcite that, 

 thickening in proportion to its distance from the surface, often 

 leaves the interstices of the latter open, while it fills those of 

 the interior, so that the fibre on the surface appears to be free ; 

 and in this white, weathered-out structure consists their great 

 beauty. Sometimes the fibre is entirely composed of linear 

 spicules overlying each other like a rope, as in Pharetro- 

 spongia Strahani^ Sollas {op. et loc. cit.), a.nd sometimes of com- 

 pact crystalline calcite, in the midst of which the spicules 

 exist like a core, as in the Farringdon specimen of Peronella 

 dtimosa. That which Prof. Zittel sent me is from the Duchy 



