1875.] DR. J. S. BOWERBANK ON THE SPONGIAD#. 293 
HALICHONDRIA PURPUREA, Bowerbank. 
Sponge massive, sessile. Surface very rough and rugged. Oscula 
simple, dispersed. Pores inconspicuous. Dermal membrane spi- 
culous ; tension-spicula fusiformi-acuate, rather slender, longer than 
those of the skeleton, very numerous; retentive spicula bidentate 
equianchorate, very minute, equable in size, numerous. Skeleton- 
rete very coarse and open; fibre multispiculous, very stout and com- 
pact; spicula fusiform acuate, short and stout. Interstitial mem- 
branes spiculous ; spicula same as those of the dermis, dispersed, 
numerous. Sarcode dark purple. 
Colour, in the dried state, dark purple. 
Hab. Straits of Malacca (Commodore Parish). 
Examined in the dried state. 
Among the sponges from the Straits of Malacca which I received 
from my friend Commodore Parish, there was a specimen of a Ser- 
tularia, on which there were four species of parasitical sponges 
located, and among them the one in course of description. It is a 
small mass about half an inch wide at the base, gradually decreasing 
in size, and terminating acutely at the height of 17 inch, of a deep- 
purple colour. The surface is remarkably rugged, full of deep pits 
and sharp elevations. The dermal membrane is very characteristic 
of the species ; it abounds in spicula ; the tension ones are frequently 
nearly twice the length of the skeleton ones, while they are very little 
more than half their diameter. They are very numerous, in some 
parts forming flat wide fasciculi, and in others they are scattered 
indiscriminately over the surface of the membrane. The retentive 
bidentate equianchorate ones are also very characteristic; they are 
Hes and delicate in form, very equable in size, and very minute ; 
they Uo not exceed ;4; inch in length, or twice the diameter of a 
fully developed skeleton-spiculum, which measured == inch in 
diameter. Nearly the whole of these spicula, seen in situ, were 
firmly attached to the surface of the membrane by the middle of the 
convex back of the shaft. They were very numerous on some parts 
of both the dermal and interstitial membranes. Occasionally a few 
also of the short stout skeleton-spicula were mingled with the tension- 
spicula of both the dermal and interstitial membranes. 
The skeleton-structure is remarkably coarse and strong, the fibre 
containing a far greater number of spicula than is usual in skeletons 
of the genus Halichondria, and the areas are wide and irregular in 
their form. These peculiarities of structure seem to indicate that 
this species attains a much greater size than the specimen under de- 
scription. The whole of the internal sarcode, as well as the external 
portions of the sponge, ‘axe of a dark purple colour. 
IsopicryA RuDIS, Bowerbank. 
Sponge massive, sessile. Surface rugged and very uneven. Oscula 
simple, dispersed, numerous. Pores inconspicuous. Dermal mem- 
brane abundantly spiculous ; tension-spicula acerate, long and slender, 
numerous, dispersed. Skeleton—texture coarse and irregular ; pri- 
