1875.] SILICEO-FIBROUS SPONGES. 507 
In my description of A. speciosum, in P. Z. S., May 13, 1869, 
p- 346, I described a small fragment of what was probably the 
dermal membrane of the sponge, beneath which the elaborate and 
beautiful defensive arrangement of spicula described in this paper 
would be situated. The account of this little fragment foreshadows 
the description of the investing animal tissues of the sponge de- 
scribed by the correspondent from the ‘Challenger,’ quoted above. 
Farrea vauipA, Bowerbank. (Plate LVII. figs. 1 & 2.) 
Sponge-mass unknown. Dermis furnished with a stout, quadri- 
lateral, smooth or, rarely, slightly tuberculated siliceo-fibrous net- 
work, armed at the angles externally and internally with short, stout, 
imbricated, conical spicular defences; areas square or slightly ob- 
long, very regular, sides of the areas abundantly armed with rectan- 
gulated sexradiate defensive organs; radii spinous; spines acutely 
conical ; fibres of the dermal rete cylindrical, very stout, eqnable in 
size, canaliculated ; canals regular, strongly produced, confluent at 
the angles. Skeleton-rete quadrangular, areas larger than those of 
the dermal network.’ Fibre smooth, not more than one third the 
diameter of those of the dermis; canals large and well developed. 
Dermal membrane obsolete. 
Colour, in the dried state, dark amber-brown. 
Hab. Unknown. 
Examined in the dried state. 
All that I know of this sponge is a piece of the dermal network a 
quarter of an inch in length by one eighth of an inch in breadth. It 
is mounted in Canada balsam. Beneath the dermal rete there is a 
small portion of the true skeleton-rete in situ. 
The specific characters derivable from the dermal structures are 
remarkably striking. The fibres of the dermal structure are com- 
paratively very large; their average diameter measured 51, inch, 
while those of the true skeleton averaged -1, inch only, and the 
central canals in both measured 3,55 inch. The fibres of the 
dermal structure are spineless; but there are occasionally a few low 
rounded tubercles dispersed on their surfaces. The mode of the 
reticulation is exceedingly regular; and the areas are all square or, to 
a slight extent, oblong, slightly curved at the angles. The conical 
spicular defensive organs at the angles are short, but very stout, and 
the imbricated scales are strongly produced. The most strikingly 
distinctive characters are the numerous rectangulated sexradiate de- 
fensive organs, based on the dermal fibres, and projected into the 
areas frequently to the extent of half their breadth. Their number 
is very considerable ; and four or five are not uncommon in a single 
area. They vary in size and form to a very considerable extent, 
some being exceedingly stout, and abundantly and strongly spinous, 
while others are slender and delicately spinous. All these organs 
appear to be furnished with a central canal; but it is frequently ren- 
dered indistinct by the profusion of spines on the surface of the 
organ, The small portion of the true skeleton does not present 
