1869.] DR. J.S. BOWERBANK ON SILICEO-FIBROUS SPONGES. 93 
with elongo-attenuato-stellate spicula, may frequently be seen in situ. 
The connecting spicula are very numerous beneath the dermal mem- 
brane of this surface, and their closely intermingled ternate heads 
form a strong and very complicated dermal network. Occasionally 
the oscula run from two or three to six or seven in a line, ona 
slightly elevated ridge ; but in other respects there is no approxima- 
tion to a definite arrangement. The pores are situated each in a single 
area, the margin of which is slightly thickened and elevated; the 
areas are visible by the aid of a lens of 2 inches focus; they are 
very numerous, and about equidistant from each other; the greater 
portion of them were in a closed condition. 
The expansile dermal system of this sponge affords excellent 
specific characters: the furcated attenuato-patento-ternate connect- 
ing spicula are large and strong, and their shafts comparatively 
long, and the central canals in both the shaft and the radii are large 
and well defined ; the fureations of their ternate heads are closely in- 
termingled, forming a fine but very irregular and complex dermal 
network. They vary very considerably in size and proportions: 
one of the largest measured {4 inch in length, and zs inch in the 
extreme expansion of its ternate head; one of the smallest measured 
zy inch in length, and in extreme expansion of its ternate head 
th inch. 
The elongo-attenuato-stellate retentive spicula of the dermal mem- 
brane are very minute ; two of the largest measured ;7,, inch and 
zosv inch in length. Their shafts are rarely straight ; they have 
usually two or three angular bends. The radii are long, slender, 
and exceedingly acutely terminated. Their structure and profuse 
dispersion on the surface of the membrane renders them a most 
effective protection against the insidious attacks of voracious enemies 
on that organ. Those on the oscular surface are larger than those 
of the inhalant one. 
The skeleton is also strikingly characteristic. The fibre is some- 
what compressed; it is perfectly smooth excepting the umbones 
with which it is studded at intervals; they project from half to once 
their own diameter from its surface, are nearly cylindrical in form, 
and have either a flat or a hemispherical apex. In the dried con- 
dition of the sponge, when closely adherent to the inner surface of 
the dermal membrane, they may at first sight be readily mistaken 
for pores ; their form and general appearance is unlike any cor- 
responding organs of a similar description in any other known species 
of this tribe of sponges. 
A few gemmules were observed; they were somewhat globular, 
with a broad attachment; with a power of 308 linear they appeared 
to be filled with minute semitransparent molecules. Their general 
character is very much that of the similar organs in Iphiteon panicea 
of the Porto-Rico specimen in the Museum of the Jardin des Plantes. 
When portions of the interior of the skeleton of this sponge are 
immersed in water, and examined beneath the microscope, the sar- 
code is found to be abundant in the interstices of the skeleton, some- 
times completely filling the interstitial spaces, and quite ignoring 
