826 
DE. J. S. BOWERBANK ON THE ANATOMY 
and the large attenuato-acuate entirely spined defensive ones in situ, X 308 
linear: page 780. 
Fig. 9. A young circular group of inequi-anchorate spicula, situated on one of the 
interstitial membranes of Hymeniacidon lingua, Boweebank, MS., X 308 
linear: page 780. 
Fig. 10. A larger and more complete circular group of inequi-anchorate spicula, con- 
taining about the usual number of spicula, from the same sponge as the group 
represented by fig. 9, x 308 linear: page 781. 
Fig. 11. A circular group of torqueato-tridentate inequi-anchorate spicula from the 
interstitial membranes of a new species of Hymeniacidon from Freemantle, 
Australia, X 308 linear: page 781. 
Fig. 12. A single spiculum, from a group similar to that represented by fig. 11, exhibit- 
ing the singular structure of the base and the tridentate apex of the spiculum, 
X 400 linear: page 781. 
Fig. 13. A section of Halichondria panieea, Johnston, showing the intermarginal cavi- 
ties at a, a, immediately beneath the dermal surface, X 108 linear : page 787. 
Fig. 14. A small portion of the dermal membrane of Tethea muricata, Bowerbank, MS., 
exhibiting the pores in an open condition, X 108 linear: page 782. 
Fig. 15. The lower portion of the same piece of membrane, highly magnified, to show 
the positions of the elongo-stellate defensive spicula on the external surface 
of the dermal membrane, X 183 linear: page 782. 
PLATE XXXII. 
Fig. 1. A section at right angles to the surface of a branch of Halichondria simulans, 
Johnston, exhibiting the form and position of the intermarginal cavities, 
X 108 linear: page 787. 
Fig. 2. A section, at right angles to the surface, of Geodia Barretti, Boweebank, MS. : — 
a, a, longitudinal sections of two of the intermarginal cavities ; b, b, the basal 
diaphragms of the intermarginal cavities ; c, c, imbedded ovaria, forming the 
dermal crust of the sponge ; d, d, the large patento-ternate spicula, the heads 
of which form the areas for the valvular bases of the intermarginal cavities ; 
e, e, e, recurvo-ternate defensive and aggressive spicula within the summits 
of the great intercellular spaces of the sponge ; f, f, portions of the inter- 
stitial membranes of the sponge, crowded with minute stellate spicula ; g, g, 
portions of the secondary system of external defensive spicula, X 50 linear: 
page 788. 
Fig. 3. View of a small portion of the inner surface of the dermal crust of Geodia Bar- 
retti, Boweebank, MS., with three of the valvular membranes of the proximal 
ends of the intermarginal cavities : — a, a, valves closed ; b, a valve partly 
open ; c, c, the radii of the patento-ternate spicula, imbedded in the tissues. 
