128 DR. J. S. BOWERBANK ON THE SPONG1AD.B. [Feb. 6, 



Fig. 4. Distal termination of one of the attenuato-expando-ternate bifurcating 

 connecting and defensive spicula, magnified 36 linear. This figure 

 represents one of the most regularly developed heads of this form of 

 spiculuin, and by no means one of the largest of them. They vary in 

 the mode and extent of the development of their radii to a very great 

 extent. 



Fig. 5 represents one of the stout elongo-stellate defensive spicula of the dermal 

 membrane, magnified 308 linear. 



Fig. 6. A small piece of the dermal membrane with the elongo-stellate spicula 

 in situ, magnified 183 linear. The recurvo-ternate spicula of Tethea 

 muricata are accurately represented by fig. 9, although the spiculum 

 figured does not belong to that species, but to T. unca. 



Tethea unca, Bowerbank. 



Fig. 7 represents the type specimen, of the natural size. 



Fig. 8. One of the fusiformi-acerate skeleton-spicula, magnified 36 linear. 



Fig. 9. A recurvo-ternate connecting and defensive spiculum, magnified 123 



linear. 

 Fig. 10. A group of three of the minute bihamate spicida from the dermal 



membrane, magnified 530 linear. 



Tethea ingalli, Bowerbank. 



Fig. 11 represents one of the largest and best-developed specimens, from Fre- 

 mantle, Australia. Natural size. 



Fig. 12. A younger specimen of the same species, from Fremantle, Australia, 

 with a gemmule attached to it. This sponge is smooth over nearly the 

 whole of the surface ; and it has an expanded concave base, having been 

 apparently attached to a smooth convex surface. Natural size. 



Fig. 13. One of the large fusil'ormi-acuate skeleton-spicula bluntly terminated, 

 magnified 80 linear. 



Fig. 14. A small fusiformi-acuate spiculum from the central mass of the sponge, 

 whence the skeleton-fasciculi emanate, magnified 80 linear. 



Fig. 15 represents one of the large subsphero-stellate spicula from the rind of 

 the sponge, magnified 530 linear. 



Fig. 16. One of the minute clavate subsphero-stellate spicula from the dermal _ 

 membrane, magnified 530 linear. This figure represents a very per- 

 fectly formed one ; they vary considerably in shape and in the clavation 

 of their radii. 



Fig. 17. An attenuato-stellate spiculum with the radii entirely and strongly 

 spined, magnified 530 linear. These spicula vary in the number of 

 their radii and in the degree of spination to a very considerable extent. 



Tethea norvagica, Bowerbank. 



Fig. 18. A small specimen of the species based on a fragment of shell, with 

 eleven gemmules in various stages of development attached to its sur- 

 face, natural size. 



Fig. 19. A well-developed specimen with six gemmules attached to it, natural 

 size. There is no apparent attachment to this sponge. 



Fig. 20 . One of the smallest specimens in my possession, attached to the re- 

 mains of the shell of a small Ealanus, natural size. 



Fig. 21. A small well-developed specimen broadly based on the surface of a small 

 stone, natural size. This sponge has thrown out broad, thin, adherent 

 plates on the surface of the stone, but they are not visible without the 

 aid of a 2-inch lens. 



Fig. 22 represents the largest specimen of the species in my possession, natural 

 size. The small mass at the base is the remains of a shell to which it 

 has apparently been attached ; the mass on the right-hand side of the 

 figure consists of two gemmules closely pressed together. 



Fig. 23. One of the skeleton-spicula, magnified 80 linear. 



