96 DR.J.S. BOWERBANK ON SILICEO-FIBROUS SPONGES. [Jan. 28, 
greatest lateral expansion ;g;7 inch; diameter of shaft g3'g3 inch ; 
length of projection of a ray zh inch; diameter of a ray 7350 
inch. The greatest disparity existing between them is not in the 
size of the shaft, or in the length of tie projection of the radii, but 
in the length of the spiculum and in the various modes of its struc- 
ture. I have been thus particular in its description because it is a 
new form of spiculum, and is especially characteristic of the species 
of the sponge in which it occurs (Plate VI. fig. 82). 
The elongo-attenuato-stellate spicula are comparatively few in 
number, and very different in their general aspect to the elongo- 
cylindrical ones. They vary exceedingly in their forms: sometimes 
they assume the shape of spiculated biternate ones; but generally 
their long, slender and attenuated radii are projected without any 
approximation to regularity. An average-sized one measured, length 
gtd inch, length of a ray rise inch, diameter of shaft z75q inch 
(Plate VI. fig. 84). 
There are also a few short cylindrical spicula, with an irregular 
inflation near the middle ; but this form is probably an undeveloped 
state of the elongo-cylindro-stellate spiculum. 
From the collapsed state of the expansile dermal system, no very 
clear view could be obtained of the investing membrane of the 
rigid skeleton ; but in sections parallel to the surface, mounted in 
Canada balsam, small portions of it were occasionally visible; and 
these appeared to be rather sparingly supplied with the elongo- 
cylindro-stellate and elongo-attenuato-stellate spicula that are so 
abundant in the dermal membrane. A few of both these forms of 
spicula are also found dispersed on the interstitial membranes. 
The long, slender and flexuous interstitial spicula occur either 
singly or in bundles of four or five together, and are usually disposed 
at nearly right angles to the surface, immediately beneath the in- 
vesting membrane of the rigid skeleton. They are very long and 
slender, and attenuate to extremely acute terminations. 
Short, stout fusiformi-acerate spicula in considerable quantities 
are sometimes found intermixed with the skeleton-fibre, immediately 
beneath the enveloping membrane of the rigid skeleton; but they 
are not found in such quantities in all parts of the sponge ; amid the 
deeper portions of the skeleton a few single ones only are occasionally 
found. A few short, stout cylindrical spicula were found among 
the spicula obtained by the dissolution of portions of the sponge in 
nitric acid ; but these are probably cases of immature development. 
The sarcode is as abundant in this as in other species of the same 
genus. Its quantity cannot be correctly appreciated in its dried 
condition, or when mounted in Canada balsam ; but in wet prepara- 
tions of portions of the skeleton, when fully expanded by moisture, 
it is in many cases to be seen completely enveloping the skeleton- 
fibre, and filling the interstices of its reticulations. 
DacTyLocALyx PoLypiscus, Bowerbank. 
Sponge irregularly cup-shaped, pedicel short. Surface even; 
sides of cup thick; margin rounded. Surface even. Oscula slightly 
