340 DR. J.S. BOWERBANK ON SILICEO-FIBROUS SPONGES. [ May 13, 
and rarely attenuato-rectangulated triradiate spicula. Retentive 
spicula attenuato-stellate, very irregular in structure, minute, very 
numerous. 
Colour in the living state unknown. 
Hah. Seychelle Islands (Capt. Etheridge, R.N.). 
Examined in the state of skeleton. 
The remarkable sponge, the subject of the present description, is 
beautifully figured in the ‘Transactions of the Linnean Society of 
London,’ vol. xxii. plate 21, as the basal mass ‘of a coarse irre- 
gular siliceous sponge,” upon which the subject of the paper, 
Luplectella cucumer, Owen, is based. The author very briefly 
notices the structure of this basal portion of his figure; and three 
small portions of its structure are represented by figures 8, 9, and 9a, 
with scarcely a sufficient amount of microscopic power to give an 
adequate idea of their structures. 
The sponge is an irregular mass, 4 inches in length by about 
21 inches in width, of siliceo-fibrous structure: about 2 inches of the 
basal portion of its length consists of a dense irregularly cylindrical 
stem about 3 inch in diameter; from its surface-structure, as seen by 
the aid of a 2-inch lens, there appears to be no doubt of its being truly 
a portion of the sponge whence it is projected. The dense structure 
and mode of projection of this indurated portion of the sponge 
renders it probable that in the living state the animal was more or 
less elevated on a pedestal. 
The greater portion of the hody of the sponge is in a disrupted 
state, apparently from compression ; but the whole of its structures 
are loosely bound together by the numerous long prehensile basal 
spicula of the Huplectella, which penetrate its substance and envelop 
it on every side. Fragments of the beautiful harrow-like tissue of 
the dermis are dispersed on various portions of the specimen; and in 
one place, partly hidden by what appears to be the small valve of a 
Terebratula, there is a portion cf the harrow-like tissue about equal 
to half or three-fourths of a superficial square inch. The general 
distribution of the fibres of the skeleton is not readily to be deter- 
mined, as the intermixture of the prehensile basal spicula of the Lu- 
plectella with its tissues is so abundant as to very much confuse its 
general aspect to the eye of an observer. The dermal structure of 
this sponge is very remarkable. It consists of a regular quadrilateral 
network of smooth siliceous fibre, from the angles of which a double 
set of short conical spiculum-shafts are projected, each about =4, inch 
in length, and entirely covered with spines. Each set are at right 
angles to the plane of the network, one series pointing inward and 
serving the purpose of attaching the dermis to the body of the sponge 
beneath, while the other set are directed outward, serving as defen- 
sive weapons; so that a small piece of this tissue beneath the micro- 
scope closely resembles an agricultural harrow, with the difference 
that it has two sets of teeth in opposite directions instead of one. 
The dermal membrane has been nearly all destroyed ; but entangled 
with the fibres of the skeleton there are some of the attenuato-stel- 
