1875.] DR. J. S. BOWERBANK ON THE SPONGIAD#. 295 
distal extremities of the branches. The skeleton-structure of this 
Species appears to be very irregular; but the well-produced primary 
lines of the skeleton unmistakably stamps it as an Isodictya. The 
rete of the dermal membrane is more or less irregular, and is, with 
its retentive spicula, very characteristic of the species. Its areas 
frequently exceed in width the length of a spiculum, and they vary 
to a considerable extent in form. The retentive spicula within them 
are in some of them rather numerous, while in others they are very 
sparingly distributed ; they are very minute and slender, requiring a 
power of about 500 linear to render them distinctly to the eye. In 
the interstitial membranes the retentive spicula are very much more 
numerous than they are in the dermal one ; and they are especially 
so in the linings of the fistulous cavities. 
It is very probable that hereafter this species will be found to 
attain a much greater altitude than the specimen in course of descrip- 
tion. I am indebted te my friend Commodore Parish for my know- 
ledge of it. He obtained it from the Straits of Malacca. 
DESMACIDON FOLIOIDES, Bowerbank. 
Sponge ramous, branches inosculating. Surface smooth, but more 
or less spiniferous. Oscula simple, dispersed. Pores inconspicuous. 
Dermal membrane pellucid, spiculous, furnished with a leaf-like 
reticulation of minute acerate spicula. Skeleton—reticulating fibres 
compact and strong; areas wide and irregular. Spicula acerate, 
rather small and short. Interstitial membranes spiculous ; tension- 
spicula dispersed, same form and size as those of the dermis. 
Colour, in the dried state, dull ochreous yellow. 
Hab. Straits of Malacca (Commodore Parish). 
Examined in the dried state. 
This sponge and a small specimen of Geodia carinata are based 
together on a little sandy mass; they are so closely incorporated, 
aud so nearly resemble each other in size, colour, and form, as to be 
readily mistaken by a hasty observer for one species only. The 
sponge-stem has an irregular expansion of 43 inches length, and 
has an average diameter of about 4 lines; one portion of the 
branches is comparatively smooth, while another portion abounds 
in spinous projections. 
The most strikingly distinctive character in this sponge exists in 
the dermal membrane. When a portion of it is mounted in Canada 
balsam and viewed with a linear power of about 100, it exhibits an 
appearance exceedingly like that of a portion of the skeleton of a 
macerated leaf of Populus nigra. There are a series of veins or long 
fasciculi composed of numerous minute acerate spicula meandering 
for considerable lengths on the inner surface of the membrane; and 
the spaces between each of these are occupied by a very delicate 
uniserial network of minute spicula, simulating in a remarkable 
manner the leafy skeleton. The skeleton-rete is very open and 
irregular, and the fibre of which it is composed is very closely com- 
pacted ; the acerate spicula of the skeleton are very much larger 
