1869.] DR. J. S. BOWERBANK ON SILICEO-FIBROUS SPONGES. 337 
These interstitial spicula are very long and are frequently flexuous, 
and are sometimes extremely numerous and closely matted together. 
In this state they have probably belonged to the expansile dermal 
system; but in the present well-washed condition of the specimen 
the true position of these matted groups could not be determined. 
The probability, however, of their having belonged to the external 
surface is increased by the presence among them of fragments of a 
thin brown membrane and numerous grains of sand. 
The skeleton-fibres are more or less spinous. The spines are acutely 
conical, and are irregularly dispersed over the surface; some parts 
of the skeleton have the fibres nearly spineless, while others are 
abundantly furnished with those minute organs. 
The spinulo-hexradiate stellate spicula are found dispersed in all 
parts of the skeleton-tissues ; but there are some little patches of in- 
termingled remains of membranes and spicula in which eight or ten 
were in close conjunction, indicating the probability that in the 
natural condition of the sponge they were very numerously dispersed 
in the membranous tissues. I counted thirty rays in some of them ; 
and we may therefore designate them as spinulo-multifurcate hexra- 
diate stellate spicula. 
The basal structure of the sponge is a remarkably beautiful tissue. 
It has on its surface an indistinct indication of irregular areas, similar 
to those of the skeleton-structure, when viewed at right angles to its 
surface ; but the spaces of the open central areas are filled up by 
plates of siliceous structure perforated by numerous round or oval 
holes. The skeleton-structure immediately above it is an irregular 
modification of the ordinary skeleton-tissues, with dense patches of 
stout acerate spicula intermixed with it. A few patches of the basal 
membranous tissue remain in situ; in its present state it is of a 
brown amber-colour ; no spicula could be detected imbedded in them. 
Kaurapsis, Bowerbank. 
Skeleton siliceo-fibrous. Basal fibres cylindrical and canaliculated ; 
distal fibres non-canaliculated, compressed. Basal reticulations sym- 
metrical and reversedly arcuate ; distal reticulations unsymmetrical 
and continuously ramifying. 
The structures of the sponge which is the type of this genus are 
remarkably anomalous, it combining in its skeleton both solid and 
eanaliculated fibre, each having a separate and distinct mode of dis- 
position in the animal. The terminations of the central canals of 
the basal cylindrical fibres are abrupt, and they are distinctly visible 
at the parts where the ramified skeleton commences. No evidence 
of central canals could be detected in any part of the upper ramify- 
ing portion of the skeleton-structure, which divides continuously as 
it approaches the surface, where the terminations spread horizontally 
in every direction, their extremities interlocking and forming a com- 
plicated and very beautiful lace-like surface to the rigid skeleton, a 
small portion of which is represented in Plate XXV. fig, 3. 
These structures, and their modes of disposition, are so remarkable 
