296 DR. J.S. BOWERBANK ON THE SPONGIADE. _[Apr. 6, 
than those of the dermal membrane; but the whole of the spicula 
are rather small, requiring a power of about 300 linear to render 
their forms and proportions distinctly. 
The interstitial membranes are abundantly supplied with acerate 
spicula irregularly dispersed, and of the same size as those of the 
dermis. I am indebted to my friend Commodore Parish for this 
interesting species. He obtained it from the Straits of Malacca. 
DESMACIDON vENUSTA, Bowerbank. 
Sponge sessile, fistulous; fistule comparatively large and open. 
Surface smooth and even. Oscula simple, within the fistulee. Pores 
inconspicuous. Dermal membrane pellucid, abundantly spiculous, 
reticulated ; rete unispiculous, very regular and beautiful; areas 
mostly triangular, rarely quadrangular ; spicula acerate, short and 
stout, same size as those of the skeleton. Skeleton-rete very diffuse 
and irregular; fibres slender and compact; spicula small, short, and 
stout. Interstitial spaces filled with beautiful masses of unispiculous 
reticulated structure; spicula same as those of the fibrous skeleton ; 
areas same size and form as those of the dermal membrane. 
Colour pale ochreous yellow in the dried state. 
Hab. Straits of Malacca (Commodore Purish). 
Examined in the dried state. 
This sponge consists of four short stout fistule, not quite an inch 
in height, the whole mass averaging about 1} inch in breadth, and 
the parietes of the fistulze are about } of an inch in thickness. The 
structural peculiarities of the dermal membrane, when a small por- 
tion of it is mounted in Canada balsam and viewed with a power of 
about 100 linear, are remarkably regular and beautiful, and espe- 
cially characteristic of the species. The rete consists of an elegantly 
symmetrical network of single spicula, with nearly the whole of the 
areas of a triangular form, a quadrangular one being of rather rare 
occurrence ; and as the component spicula are very equal in their 
lengths and diameters, the result is a remarkable degree of sym- 
metry and beauty. The whole of the interstitial spaces within the 
fibrous skeleton are filled with masses of a similarly regular and 
beautiful unispiculous reticular structure, closely simulating that 
of the dermal structure ; and amidst this beautiful tissue the long, 
slender, fibrous skeleton meanders in various directions. Although 
the structural characters of this species are few and simple, the 
regularity and beauty of the modes of their disposition afford ex- 
cellent specific characters for its identification. The only species of 
Desmacidon with which it might possibly be confounded is D. fo- 
lioides, from the same locality ; but, independent of the differences of 
external form, the last-named species differs in the dermal mem- 
brane being furnished with the peculiar leaf-like arrangement of its 
rete, and in the interstitial spaces; the spicula are only sparingly 
dispersed on the membranes. In both species the spicula are of 
about the same length ; but those of the species in course of descrip- 
tion are twice the diameter of those of D. folioides. 
