362 DR. J. S. BOWERBANK ON Nov. 2, 
rally to be two layers of skeleton-structure; and occasionally a por- 
tion of a third layer may be seen between them; and this inter- 
mediate one appears to be very much less regular in its structure 
than either of the other two. The acutely conical spines on the 
fibres are not equally dispersed ; on some parts they are very nume- 
rous, while on others they are much less in number. The aculei 
are very characteristic organs. They are of unequal length, and ir- 
regular in their mode of disposition. On some fibres a single one is 
projected ; on others there are two on opposite sides of the fibre; 
and sometimes there are three or four developed in direetions op- 
posite to each other. ‘hey are rather slender, and attenuate gra- 
dually from the base to the distal extremity, which is frequently 
very slender and acnte. The rectangulate sexradiate defensive 
organs are numerous ; they are of nearly equal size, and are disposed 
irregularly among the fibres ; but they are mostly projected into the 
square areas of the skeleton-rete. The canals in the skeleton-fibres 
are very slender, and in many of the large ones they are partially or 
entirely obsolete. 
I know of no other species for which F’. aculeata might be readily 
mistaken except F’. spinifera. The former species differs from the 
latter in the smallness and very much less-developed state of the 
canaliculation of its fibres, and in the far greater development of 
the minute spination of its skeleton—also in the abundance in the 
former species of the rectangulate sexradiate internal defences, 
while in the latter they appear to be totally absent. 
FarreEa rosusta. (Plate LXII. figs. 2-6.) 
Sponge—form cup-shaped? surface minutely hispid. Oscula and 
pores unknown. Dermal membrane thin and pellucid, abundantly 
spiculous ; tension-spicula long and very’ slender, subclavate, cylin- 
drical, very few in number; retentive spicula simple and contort, 
bihamate, small and slender, dispersed, rather numerous, and biden- 
tate equianchorate small and few in number ; furnished also with 
numerous internal defensive spicula of subspinulate, attenuato- 
acuate forms, entirely incipiently spinous, projected at various 
angles from the inner surface of the membrane. 
Skeleton—fibres very large and strong, cylindrical, sparingly 
spinous or aculeated ; aculei short and slender, dispersed ; armed 
abundantly with rectangulate sexradiate defensive organs, radii 
slender, attenuated, incipiently spinous. Rete more or less quadran- 
gular, areas frequently very little more in breadth than the diameters 
of the skeleton-fibres. Central canals small. 
Colour, in the dried state, dark amber. 
Hab. West Indies (Captain Hunter, R.N.?). 
Examined in the skeleton state. 
I have seen only a single specimen of this remarkable sponge. It 
was given, with other specimens, by the late Mr. Henry Deane to my 
friend Captain Charles Tyler, who kindly presented it to me for de- 
scription and publication. It consists of a thin plate of siliceo-fibrous 
