1875. SILICEO-FIBROUS SPONGES. 559 
it to Farrea until further information on the subject enables us to 
assign it more correctly to its proper place among the siliceo-fibrous 
sponges. 
The primary skeleton-fibres are large and cylindrical, but of un- 
equal diameter, and mostly have the appearance of transparent lon- 
gitudinal striation from their strongly marked lines of growth, and 
they are more or less minutely spinous; their course is irregular, 
not running in straight lines, but in meandering ones, branching at 
intervals and again anastomosing with each other. Their large 
conical defensive organs are not all systematically projected outwards 
at about right angles to the dermal surface; some are so disposed, 
while others have a lateral direction, or are projected at various in- 
termediate angles. 
The central system of canals in the primary fibres is subject to 
considerable irregularity. Sometimes they are regularly confluent ; 
at others they are produced in opposite directions, and their distal: 
ends pass each other, and each has a cecoid termination. It is net 
an unusual circumstance to see a short sexradiate arrangement of 
canals within one of the large fibres, as if the process of the produc- 
tion of new branches was first, the development of the canals within 
the parent fibre, and then the projection of the young offshoots in 
accordance with the nascent canals. In some cases there is not the 
slightest indication on the surface of the large fibre of the coming 
offshoot, while in others there is a very slight elevation on its sur- 
face immediately above the nascent canal; or the young shoot, in 
the form of an acutely conical projection, is unmistakably present 
with the continuation of the canal in its centre to its apex, where it 
usually appears to be open in the early stage of its development, 
with extremely delicate margins; but in a more advanced stage of 
its growth the apex becomes solid. These projections of young 
branches are readily to be distinguished from the conical external 
defences by their canals, while the defensive organs appear to be per- 
fectly solid. 
The inner external surface has the same characters as the outer 
one, but the dermal skeleton-fibres seem to be rather more slender. 
The intervening skeleton is more regular in its construction than the 
external layers. The reticulation is more regularly quadrate and 
the areas smaller. The fibres are also smaller and more profusely 
spinous; and the central canals are more continuous and confluent than 
those of the fibres of the external surface, and in some parts they 
are densely coated with dark-coloured opaque sarcode. I could not 
detect the slightest traces of any detached spicula amidst the struc- 
tures. 
This interesting specimen is in the cabinet of my friend Mr. H. 
Deane, who, I believe, received it with other specimens from Captain 
Hunter, R.N. 
Since the above description was written, I have received another 
specimen of this species from my friend Mr. Deane. It is about 
four lines square, and is closely attached by one of its broad surfaces 
to the side of a small fragment of a Vermetus, and does not exhibit 
Proc. Zoou. Soc.—1875, No. XXXVI. 36 
