the Greensand compared with those of existing Species. 121 



history ; but at present I know of no moniliform spicules 

 having curved, cylindrical, and quadiradiate forms respec- 

 tively to which they can be likened. 



Fig. 54 appears to have been one of the curved cylindrical 

 spicides which has suffered from erosion, and thus shows the 

 effect of the solvent power, which may thus be infeiTcd, not 

 only to have fretted out partially, but to have fretted away 

 altogether many of the spicules that were originally in this 

 deposit. Indeed we cannot have a more satisfactory example 

 of this power than in fig. 70, which shows a very common 

 occurrence in the Haldon deposit, viz. the bare extension of the 

 axial canal in a consolidated state beyond the rest of the fossil 

 shaft or spicule, which has thus evidently been removed by 

 some solvent influence. 



The remainder of the small spicules here represented are 

 abundantly present in the deposit, but more remarkable for 

 their multiplicity than for any peculiarities by which they 

 could be identified witli. existing species ; they represent the 

 smallest spicules of the mass, and those forms which perhaps 

 are most abundant, but by no means all the varieties which 

 are present. In many instances the chalcedonizing influence 

 has so firmly united them, as well as the little globular 

 crystalloids of the Geodidai, to the larger spicules, especially 

 to the fragments of silicified fibre from the Coralliospongias 

 (see figs. 19, 20, and 24), that they cannot be detached with- 

 out fracture of the latter ; but it does not follow from this that 

 such small spicules have ever formed part of the sponges 

 from which the large fragments or spicules to which they now 

 adhere were derived. They were thrown together at the time 

 of deposit, and became adherent afterwards. I have frequently 

 destroyed a fine large spicule by endeavouring to detach the 

 small ones from it. 



Among the small spicules, however, are some pointed at 

 one end and truncated at the other, as if fractured at this part, 

 which appear to have originally belonged to the silicified fibre 

 of the Coralliospongise ; for such are occasionally seen to be 

 not merely adherent to the fragments of this fibre, but actually 

 with one end imbedded in it for some distance (figs. 25 and 28), 

 just as with the Ajjhrocallistes, for a good example of which 

 see Bowerbank's illustrations (Proceed, cit. 1869, pi. xxi. 

 figs. 2, 3, and 4). The specimen of Aphrocallistes Bocagei, 

 which was examined by Schmidt, was found by M. de Pour- 

 tales on a reef in the Grulf of Florida, 283 fathoms deep 

 (Atlant. Spong. Faun.). 



So long as we are content with the coarser features of the 

 larger spicules of the Spongiadae contained in the Haldon de- 



Ann. (k Mag. N. Hist. Ser. 4. Vol. r'n. 9 



