J873.] DR. J. S. BOWERBANK ON THE SPONGIAD^E. 23 



Fig. 3. A large bifurcated patonti-ternate connecting spiculum, magnified SO 



linear. 

 Fig. 4. The apes of a large-sized bifurcated patenti-ternate connecting spiculum, 



magnified 80 linear. 

 Fig. 5. A small simple attenuated expando-ternate connecting spiculum, magni- 

 fied SO linear. 

 Fig. 6. A young expando-ternate bifurcating connecting spiculum, exhibiting 



the gradual development of the bifurcations of the ternate radii, ma". 



nified 10 linear. 

 Fig. 7. One of the recurvo-ternate spicula, magnified 80 linear. 

 Fig. 8. A porrecto-ternate spiculum, magnified 80 linear. 

 Fig. 9. A large attenuato-subsphero-stellate retentive spiculum, magnified 530 



linear. 

 Fig. 10. One of the minute cylindro-stellate retentive spicula, magnified 530 



linear. 

 Fig. 11. A minute slender acerate tension-spiculum from the dermal membrane, 



magnified 80 linear. 



Tethea robusta, Bowerbank. 



Fig. 12. A section at right angles to the surface of T. robusta, from the type 

 specimen in the British Museum : natural size. 



Fig. 13. One of the skeleton-spicula from the large fasciculi, magnified 80 

 linear. 



Fig. 14. A smaller skeleton-spiculum from the central nucleus, magnified 80 

 linear. 



Fig. 15. One of the very large sphero-stellate spicula of the dermal rind, mag- 

 nified 530 linear. 



Fig. 16. A small cylindro-spbero-stellate retentive spiculum from the interstitial 

 membranes, magnified 530 linear. 



Fig. 17. One of the minute clavated cylindro-stellate spicida from the intersti- 

 tial membranes, magnified 530 linear. 



Geodia inagualis, Bowerbank. 



Fig. 18. The type specimen, natural size. 



Fig. 19. One of the inequicylindrical skeleton-spicula, magnified 80 linear. 



Fig. 20. An expando-ternate connecting spicidum with the shaft slightly curved, 

 magnified 80 linear. 



Fig. 21. A large attenuato-multiradiate retentive spiculum from the interstitial 

 membranes, magnified 530 linear. 



Fig. 22. An attenuato-subsphero-stellate retentive spiculum from the interstitial 

 membranes, magnified 530 linear. 



Fig. 23. One of the minute cylindro-subsphero-stellate spicula from the inter- 

 stitial membranes, magnified 530 linear. 



Geodia media, Bowerbank. 



Fig. 24. The type specimen, natural size. 



Fig. 25. One of the short stout acerate skeleton-spicula, magnified 80 linear. 



Fig. 26. An expando-ternate connecting spiculum, magnified 80 linear. 



Fig. 27. A midtiradiate attenuato-stellate retentive spiculum from the intersti- 

 tial membranes, magnified 530 linear. 



Fig. 28. A minute cylindro-stellate retentive spiculum from the interstitial mem- 

 branes, magnified 530 linear. 



Fig. 29. A doliolate spiculum from the interstitial membranes, magnified 150 

 linear. These spicula are very few in number, and vary to some extent 

 in their shape and size. 



Plate III. 



Geodia Dysoni, Bowerbank. 

 Fig. 1 represents the type specimen, natural size. 

 Fig. 2, One of the fusiformi-acerate skeleton-spicula, magnified 80 linear. 



