200 Dr. G. J. Hinde on Fossil Calcispongie. 
It is only by careful search that the small spicules just 
mentioned can be singled out in the confusedly mingled mass 
of spicular forms present in the fibre; the general appearance 
of the fibre is that of numerous very fine, sinuous, interrupted 
lines, which run parallel with the direction of the fibre, and 
are closest arranged near the margins. I have been unable 
to determine satisfactorily the character of these minute wavy 
lines. In part they appear to be formed by the closely inter- 
lacing rays of irregularly fork-shaped spicules similar to that 
represented in fig. 6; but they may also indicate the bisected 
outlines of very minute spicules which are so interwoven and 
dovetailed into each other that the separate forms cannot be 
distinguished. In the recent sponges Leucandra Johnstonit, 
Carter, sp. (Ann. & Mag. Nat. Hist. 1871, vol. viii. p. 3, t. 1. 
figs. 5-12), and Leucandra stilifera, O. Schmidt, sp. (Atlan. 
Spong. p. 73, t. 2. fig. 24), and some other forms as well, the 
skeleton is in part composed of relatively very large quad- 
riradiate and very minute uniaxal and quadriradiate spicules. 
Hackel states (Mon. Bd. ii. p. 225) that in the last-named 
species, L. stilifera, the minute uniaxal spicules are mixed 
up together in masses which may be compared to stucco or 
mortar, which covers the smooth dermal and gastral surfaces, 
and envelops and connects together the large and colossal 
quadriradiates which form the scaffolding of the skeleton. It 
seems to me probable that in this fossil species the large 
quadriradiate spicules of the centre of the fibre are similarly 
enveloped by minute spicules, and that the minute wavy 
lines seen in the thin microscopic section may be the outlines 
of a compact felted mass of these diminutive bodies. 
The tri- and quadriradiates of this fossil are precisely 
similar in form to spicules met with in several species of 
Hickel’s recent genus Leucandra; but in respect of their 
dimensions, the largest fall short of the size of some of the 
spicules of the recent sponges. The pickaxe spicule (fig. 8) 
and fork-shaped spicules (figs. 6, 12-15) are more specialized 
and restricted forms, consequently of greater value for com- 
parison ; for if these very peculiar types occur in recent Calci- 
sponges, but little doubt can be entertained of the calcareous 
origin of the fossil sponges. It is therefore satisfactory to 
find that spicules of similar form are present in the skeleton 
of two recent species of calcareous sponges, Leucetta pandora, 
Hick. (Mon. Bd. ii. p. 127, Taf. xxi. f. 3 a—c, Taf. xxiii.), 
and Leucortis pulvinar (Hick. p. 166). Similar spicules 
were first figured by Bowerbank (Mon. Brit. Spong. vol. 1. 
p- 268, pl. x. f. 237) from a calcareous sponge from Free- 
mantle, Australia. On these, Gray founded a new genus and 
