290 DR. J. S. BOWERBANK ON THE SPONGIADZ. __[Apr. 6, 
they are about as numerous on the interstitial membranes as on the 
dermal one. The bidentate equianchorate ones are rather rare ; 
they are not readily found in stu amidst the numerous minute 
grains of sand adherent to the membranes; but they are readily 
found among the spicula prepared by the aid of nitric acid, but they 
require the application of a power of about 400 linear to render them 
distinctly to the eye; they are stout and short in their proportions. 
The interstitial membranes are usually rather sparingly spiculous ; 
but occasionally the spicula are clustered together in considerable 
quantities. 
HALICHONDRIA CRASSA, Bowerbank. 
Sponge massive, sessile. Surface uneven and very rugged, with 
numerous irregular thin ridges and elevations, coarsely reticulated. 
Oscula simple, dispersed. Pores inconspicuous. Dermal membrane 
spiculous ; tension-spicula acuate, same size and form as those of the 
skeleton, not very numerous ; retentive spicula, two descriptions of 
bihamate, simple and contort, large and small, and bidentate equi- 
anchorate minute, and few in number. Skeleton-rete multispicu- 
lous, coarse, and strong; areas large and irregular ; spicula acuate, 
rather short and stout. Interstitial membranes spiculous ; spicula 
same as those of the dermis. 
Colour, in the dried state, dull pale green. 
Hab. Straits of Malacca (Commodore Parish). 
Examined in the dried state. 
I received a single specimen of this sponge from my friend Com- 
modore Parish, who obtained it from the Straits of Malacca. Itisa 
rough-looking mass, very irregular in form, about 13 inch in dia- 
meter, and half an inch in thickness, and it has several specimens of 
Balanus imbedded in its substance. Its surface is full of sharp, thin, 
elevated ridges and deep depressions ; and all parts of its surface are 
coarsely reticulated, the reticulation being more or less visible to the 
unassisted eye, and very apparent by the aid of a lens of 2 inches 
focus. This coarse reticulation arises in the dried specimen from 
the very coarse and open character of the skeleton-structures imme- 
diately beneath the dermis. 
The oscula are rather numerous; and some of them exceed a line 
in diameter. The dermal membrane is in some parts rather sparingly, 
and in others profusely, furnished with its respective spicula; the 
tension ones, like those of the skeleton, are purely acuate. Of the 
bibamate retentive spicula there are two distinct sizes—one com- 
paratively large (that is to say, measuring on an average ;1, inch in 
length), while the minuter set of these forms measured only 55; inch 
in length. These minute forms could not be detected in situ ; but in 
the remains of the membranes rendered transparent by the action of 
nitric acid and mounting in Canada balsam, and with a power of 
about 700 linear, they were distinctly visible. The bidentate equi- 
anchorate retentive spicula were also minute ; they varied in length 
from yo; inch to <4, inch, and required a power of about 400 
