36 On the so-called u Farringdon Sponges" 



lites anastomans was confronted by pinlike spicules situated 

 in the outer layer of calcite, with their points directed inwards 

 towards the core of triradiates, and their heads outwards. 



Now, as I have long since asserted — and have endeavoured 

 subsequently to show in Bhaphidotheca Mars hall- Hall ii, Kent 

 ( c Annals,' 1878, vol. i. p. 170 ; and Journ. Koy. Microscop. 

 Society, 1879, vol. ii. p. 497, pi. xvii. a) — that the points and 

 not the heads of spicules are always directed outwards in the 

 Spongida when they have been formed by the sponge itself, 

 it follows that these little pinlike spicules have, in all proba- 

 bility, been in like manner appropriated by the Verticillites, 

 and therefore form no part of its original spiculation. 



But as no pinlike spicules have ever been found among 

 existing Calcispongia?, while they are abundantly present 

 among the Silicispongi^e, it also tends to the conclusion that 

 these were also siliceous, but have been transformed into cal- 

 cite by the calcareous lye which, as I have before stated, in 

 most instances half dissolved the spicules of the Calcisponge 

 itself. 



These pinlike spicules are about 30-6000ths inch long by 

 l-6000th inch thick in their greatest dimensions, and in 

 appearance very much like those of Terpios fugax { c Annals/ 

 1882, vol. ix. p. 355, pi. xii. fig. 29) ; only the latter are a 

 little thinner and longer, besides being slightly curved, which 

 the former do not appear to have been. This sponge, or one 

 allied to it, might, as it is of extreme thinness, have been 

 supposed to have grown over the surface of the Verticillites } 

 as it is its wont to do over corals &c. of the present day ; but 

 then the points would have been outwards, which is not the 

 case in Dr. HolPs specimen. They are not figured by Dr. 

 Hinde as present in his Verticillites D* Orbignyi • nor have I 

 seen such in my specimens of Verticillites anastomans from 



Farringdon. 



N.B. 



EXPLANATION OF PLATE I. 



on the scale of l-48th to l-1800th 

 3th to 1-G000th : No. 13. maamified m 



a diagram on the scale of l-24th to l-1800th; Nos. 16 and 17, on the 

 same scale, viz. l-48th to 1 -6000th inch, to show their sizes relatively. 



Scyphia cylindrica 

 Natural size. 



Lateral 



Fig. 2. The same. Aperture of cloacal canal. (This is grooved in some 



specimens and plain in others. Nat. size.) 

 Fig. 3. The same. Vertical section of the lower third, showing the end 



of the cloacal canal and the larger branches of the excretory 



system which opened into it. Nat. size. 

 Fig. 4. The same. Fragment of the fibre, as seen in a polished surface of 



the fossil under a microscopic power of about 150 diameters. 



