824 
DE. J. S. BOWEEBANK ON THE ANATOMY 
Fig. 2. A spinulate spiculum from Halicnemia jpatera^ Boweebank, MS., xl75 linear: 
page 766. 
Fig. 3. A bispinulate spiculum from the same sponge, Xl75 linear: page 766. 
Fig. 4. A trispinulate spiculum from the same sponge, Xl75 linear: page 766. 
Figs. 5, 6, 7. The same forms of spicula as figures 2, 3, and 4, in progressive stages of 
development, the apices not having attained their acute terminations, xl75 
linear: page 766. 
Fig. 8. Inner surface of the dermal crust of Dactylocalyx Prattii, showing the manner 
in which the apices of the radii of the ternate spicula are spliced on each other 
to form the areas for the intermarginal cavities, xl08 linear: page 767. 
Fig. 9. Three of the ternate spicula of Pactylocalyx Prattii, exhibiting the variations 
in form and the compressed condition of their radii, Xl08 linear: page 767. 
Fig. 10. A portion of a thin section at right angles to the surface of a specimen of 
Halichondria seriata, Johjstston, illustrating the mode of external defence by 
the prolongation of the radial lines of the skeleton, Xl08 linear: page 769. 
Fig. 11. Part of a small branch of Piety ocylindrus rugosus, Boweebaxk, MS., exhibiting 
the radiating structure of the defensive fasciculi, x50 linear: a, a part of 
the central axis of spicula: page 770. 
Fig. 12. A portion of a slice at right angles to the surface from Tethea cranium, showing 
the fasciculi of defensive spicula {a), and the mode in which they are supported 
by buttresses of spicula beneath the surface of the sponge at : c, the recurvo- 
ternate spicula, x50 linear: page 770. 
PLATE XXX. 
Fig. 1. A section at right angles to the surface of Microciona atrosanguinea, Boweebank, 
MS., showing the position of the pedestals forming the skeleton and the 
terminal spicula, Xl08 linear: page 771. 
Fig. 2. A single mature pedestal, showing its structure and the proportions and posi- 
tions of the external defensive spicula, Xl75 linear: page 771. 
Fig. 3. A section of Hymerajyliia stellifera, Boweebank, MS., showing the large bulbous 
skeleton-spicula in situ, their apices forming the external defences: a, the 
stelliferous internal defensive spicula elevated by a grain of sand beneath the 
basal membrane, Xl08 linear: page 771. 
Fig. 4. a. The basal portion of one of the skeleton-spicula of HymerapMa stellifera, with 
its large bulbous base, X 260 linear: h, one of the stelliferous internal defen- 
sive spicula, x260 linear: page 771. 
Fig. 5. A small portion of a longitudinal section through the cloaca of a specimen of 
Grantia tessellata, Boweebank, MS., showing the positions of the internal 
defensive spicula, and their curvature towards the mouth of the cloaca, Xl08 
linear: page 772. 
