1869.] DR. J.S. BOWERBANK ON SILICEO-FIBROUS SPONGES. 99 
Fig. 10. A dichotomo-patento-ternate connecting spiculum from the type spe- 
cimen, magnified 108 linear. 
Fig. 11. Minute attenuato-stellate retentive and defensive spicula from the type 
specimen, magnified 666 linear. 
Fig. 12. A gemmule adhering to auxiliary fibres of the skeleton from the large 
specimen of D. pwmiceus (Iphiteon panicea, Valenciennes) in the col- 
lection of the Jardin des Plantes, Paris, magnified 108 linear. 
Fig. 13. A profile view of two of the tubercles on the skeleton-fibre of the type 
specimen of D. pumiceus, exhibiting the papillation of their summits, 
magnified 666 linear. 
Figs. 14 & 15. Portions of the densely reticulated basal skeleton-structure from 
the type specimen, magnified 108 linear. 
Fig. 16. Trifurcated expando-ternate connecting spicula, probably belonging to 
an unknown species of Dactylocalyx, magnified 666 linear. 
Puate IV. 
Fig. 1. A portion of the rigid skeleton of Dactylocalyx heteroformis (Coscino- 
spongia heteroformis, Valenciennes), exhibiting the complicated reticu- 
lations of the structure, and the ramified free terminations of the 
fibres, magnified 175 linear. 
Fig. 2. One of the large incurrent areas of the inhalant surface of the same 
sponge, exhibiting the protective furcated terminations of the marginal 
fibres, magnified 308 linear. 
Fig. 3. One of the oscula from the exhalant surface of the same sponge, exhibiting 
the oscular membrane in a half-open condition, magnified 183 linear. 
Fig. 4, A portion of the dermal membrane of D. heteroformis, with its fine but 
very irregular network of siliceous fibre, magnified 308 linear. 
Fig. 5. A portion of the dermal membrane of Dactylocalya MeAndrewii (Mac- 
: Andrewia azorica, Gray), exhibiting the ramifications of the foliato- 
expando-ternate connecting spicula beneath, and one of the inhalant 
pores with its defensive system of minute acerate dermal spicula, 
magnified 183 linear, 
Puare VY. 
Fig. 1. A portion of the rigid skeleton of Dactylocalyx MeAndrewii, magnified 
175 linear. 
Fig. 2. A foliato-expando-ternate connecting spiculum from the expansile 
dermal system of D. MeAndrewii, with the inner surface towards the 
eye exhibiting the short acutely conical shaft of the spiculum, magni- 
fied 175 linear. 
3. An elongated and’ more ramose variety of the ternate head of the same 
sort of spiculum as that represented by fig. 2, magnified 175 linear. 
Fig. 4. A view in profile of a spiculum of the same form as those that are re- 
presented by figs. 2 & 3, magnified 175 linear. 
5. One of the minute fusiformi-acerate tension-spicula of the dermal 
membrane of D. M¢Andrewii, magnified 666 linear. 
6. A section at right angles to the surface of D. Prattii, exhibiting a portion 
of the expansile system (a) in a state of separation from the rigid 
siliceo-fibrous skeleton beneath, with the shafts of the connecting 
spicula pendent in the space between them, and also the primary 
dermal membrane, and the secondary membrane covering the external 
surface of the rigid skeleton filled with the innumerable retentive 
spicula of those organs, magnified 108 linear. 
Fig. 7. Two of the retentive spicula of the dermal membrane and the investing 
membrane of the rigid skeleton, magnified 1250 linear. 
Fig. 8. A view of the inner surface of a portion of the expansile dermal system, 
exhibiting the interlacing of the radii of the irregularly furcated 
patento-ternate connecting spicula to form the inhalant areas, in 
which are situated the pores of imbibition, magnified 108 linear. 
Figs. 9, 10, & 11. Three of the irregularly furcated patento-ternate connecting spi- 
cula, exhibiting their extreme diversity of form, magnified 108 linear. 
