1869,] DR. J. S. BOWERBANK ON SILICEO-FIBROUS SPONGES. 85 
were observed ; but their absence may be readily accounted for by 
the condition of the basal portion of the French specimen and the 
apparently total destruction of its dermal membrane. In every 
other specific character there is a complete agreement between the 
two specimens under consideration. 
Among the spicula resulting from the dissolution of a portion of 
the basal structures of the type specimen of D. pumiceus, I found two 
trifurcated expando-ternate spicula, which are represented by fig. 14, 
Plate III., x 666 linear. They are very minute, and probably 
belong to an unknown species of the genus, and were adherent to the 
basal membrane of D. pumiceus. I have never met with this form 
of spiculum before ; I have therefore thought it advisable to record 
its occurrence. 
DactTyLocaLyX HETEROFORMIS, Bowerbank. 
Coscinospongia heteroformis, Valenciennes. 
Sponge sessile, fan-shaped, plicated sinuously. Surface slightly 
undulating, minutely hispid. Oscula on the upper surface slightly 
elevated and marginated, margins rounded; uniform in size and 
very numerous, irregularly dispersed, rarely exceeding one-third of a 
line in diameter. Pores congregated on the under or inhalaut 
surface ; porous areas scarcely visible to the unassisted eye, slightly 
depressed, very numerous, dispersed, rarely more than once their 
own diameter from each other. Expansile dermal system exceed- 
ingly ramified and complicated ; inhalant surface furnished abun- 
dantly with long, slender, flexuous spicula, irregularly dispersed amid 
the dermal fibres. Dermal membrane pellucid, furnished with a fine 
but very irregular network of apparently siliceous fibres. Skeleton 
—reticulations close, irregular, and very much ramified ; fibre smooth, 
slightly compressed ; frequently terminating in dense short tufts of 
minutely ramified fibres. 
Colour in the dried state, dark brown. 
Hab. Shanghai (M. Montigny, 1854). 
Examined in the dried condition. 
The sponge is composed of numerous sinuous plications or folds 
from 3 to 4 lines in thickness near the margin. It is 5 inches in 
height, 43 inches in breadth, and, including the plications, from 3 to 
4 inches from back to front. The membranous and sarcodous tis- 
sues are apparently in the same state of preservation as when taken 
from the sea in a living condition. The surface of the plications is 
slightly undulated. The hispidation of the surface is not visible to 
the unassisted eye; but, in a section at right angles to the surface, 
beneath the microscope it is distinctly apparent. The integral parts 
of the expansile dermal system appear to be inextricably locked to- 
gether; but this external layer of tissue is distinctly separated from 
the solid mass of the skeleton beneath it. The porous system on 
the under or inhalant surface of the sponge is a very beautiful mi- 
croscopical object. The inhalant areas are exceedingly numerous 
and closely adjoining each other ; they vary to some extent in their 
