Spongia coriacea of Montagu. 27 



B. W. Priest in September 1882, when I thought, from their 

 resistance and apparent durability on being handled, that 

 had I been acquainted with them earlier I should never have 

 discredited the fact that a calcisponge could be fossilized. 

 Thinking, however, from their resemblance that thej were 

 specimens of Leucosolenia lacunosa, I put them aside under 

 this belief; but lately I have had to examine them in con- 

 nexion with the foregoing species, viz. Clathrina coriacea^ 

 and then I perceived that the solidity of the stem and its 

 spicular composition were like the fibre of Peronella muUi- 

 digitata^ Zittel, of ? Scyphia perplexcij Quenstedt (tab. 125. 

 fig. 63), and of Manon peziza, also Quenstedt (t. 182. fig. 30), 

 respectively ; that is, that it was composed of triradiates in the 

 centre faced by a layer of linear and vermiform spicules, each 

 of which indicated by the kind of 7iode mentioned (PL I. 

 fig. 5, ccc) near the centre, which slightly projects, that it 

 represented the aborted state of a third ray, and thus a modi- 

 fication of the triradiate. 



Now, when we consider that the stem, as it approaches the 

 body (PI. I. fig. 2, «rZ), divides into a multitude of branches, 

 each of which, although solid in the first instance, becomes 

 transformed into a tahe to form the tubular thread of the body 

 (fig. 2, /) , which by branching and anastomosing produces the 

 clathrous structure in which the linear and vermicular spicules 

 are entirely abseiit, and that the linear and vermicular spicules 

 thus cease to appear where the transformation takes place^ it fol- 

 lows that had the branches continued so/iVHike the thread of the 

 clathrous structure in Leucetla dathrata, Gxiw {pp. et loc.cit.), 

 they would have been identical in spicular composition and 

 arrangement with the fibre of the fossils mentioned, where, on 

 account of their contortion being perhaps more generally 

 greater than that in Leucosolenia lacunosa, var. IliUieri^ the 

 extreme thinness of the microscopic slice cutting oif the bends 

 above and below, seldom allows one to be seen entire. Indeed 

 the more contort ones in Leucosolenia Hillieri during the 

 boiling out in liquor potassa3, from this together with the 

 brittleness of the material, for the most part, come out broken. 

 Thus the " filiform spicules " of the fossil Calcispongige seem 

 to be elucidated. 



Pin-like Spicules (? parasitic) on Verticillites anastomans 

 and A. helvetica. (PI. I. figs. 6-10.) 



At the conclusion of my paper on the Fossil Calcispongiaa 

 of Faringdon ('Annals,' 1883, vol. xi. p. 33) I had only 

 just time to mention Dr. Harvey B. Roll's discovery of pin- 

 like spicules in that variety of Verticillites designated " helve- 



