1869,] DR, J.S, BOWERBANK ON SILICEO-FIBROUS SPONGES. 339 
cylindrical spicula, which had every appearance of belonging to the 
dermal membrane. With this indication, I mounted all the remain- 
ing fragments of the sponge in my possession, and I was fortunate 
enough to find a small piece of dermal membrane crowded with these 
minute spicula, and having several of the foliato-peltate spicula 
attached to its under surface, thus leaving no doubt remaining re- 
garding the presence and nature of the expansile dermal membrane 
of this singular and beautiful species of siliceo-fibrous sponge (Pl. 
XXV. fig. 4). 
The specific characters of the sponge, although few in number, 
combined with the peculiar and very striking ones derivable from the 
skeleton, which I have described in detail in treating of the genus, 
enable us readily to distinguish the species from any other siliceo- 
fibrous sponge. The cidarate prehensile fibres at the base of the 
sponge are remarkably curious organs ; they proceed at right angles 
from the crowns of the reversed basal arches, and terminate in stout 
and acute cones; and intermediate between their origins and termi- 
nations each has a ring of stout round bosses admirably fitting them 
first to penetrate the fleshy external coat of the coral, and, when once 
inserted, to securely maintain their position. There is no mistaking 
the office of these curious and beautiful organs and the admirable 
adaptation to the nature of the basis on which they were destined to 
be parasitic (Pl. XXYV. fig. 2). 
The forms of the foliato-peltate heads of the connecting spicula 
are exceedingly various, passing through every gradation from simple 
circular plates to the most elaborate foliations. On some of the 
heads of the detached spicula groups of three or four of the minute 
fusiform-cylindrical retentive and defensive spicula were attached ; 
but on some parts of the small fragment of the dermal membrane 
they were so numerous and so crowded together as to render their 
individual forms perfectly undistinguishable. The membrane is of 
a dark brown colour, and can scarcely be said to be transparent, in con- 
sequence of the number of the spicula and the density of the sarcode 
in which they are imbedded. I measured some of the largest and 
smallest of them, and found their average length not to exceed 545 
ae The greatest diameter of a large one was gj55 inch (Pl. XXV. 
g. 5). 
In these minute spicula the central canal was visible with a linear 
power of 666 throughout the whole of their lengths, and it occupied 
about one-sixth of the greatest diameter, so that its own diameter 
could not exceed about ;¢);5 inch. 
FarREA occa, Bowerbank. 
Sponge massive, pedicelled? Surface even? minutely hispid ? 
Oscula and pores unknown. Dermis furnished with a quadrilateral 
smooth siliceo-fibrous network, armed at the angles oppositely, ex- 
ternally and internally, with short imbricated conical spicular de- 
fences. Skeleton—rete irregularly quadrilateral ; fibre cylindrical, 
more or less minutely tuberculated or spined. Tension-spicula 
biternate, spiculated biternate, and furcated spiculated biternate, 
