PLATE XVII. 



" RAPHIODESMA INTEEMEDIUM, Bowerbank. 



Figs. 1 and 2. Represent the type-specimens of 

 the species. Natural size. 



Fig. 3. A small portion of the dermal membrane 

 exhibiting the structure of the dermal rete and the 

 mode of the disposition of the bihamate retentive 

 spicula. X 160 linear. 



Fig. 4. An average-sized skeleton spiculum. X 

 264 linear. 



Fig. 5. One of the long and slender tension 

 spicula of the interstitial membranes. X 264 linear. 



Fig. 6. A contort, biharnate, retentive spiculum 

 from the dermal membrane. X 264 linear." 



" RAPHIODESMA FALLACIOSUM, Bowerbanfc. 



Fig. 7. Represents the shell of Pecten varius with 

 the type-specimen of the sponge upon it opposite a. 

 Natural size. 



Fig. 8. One of the long and slender acuate spicula 

 of the dermal fasciculi. X 264 linear. 



Fig. 9. A dentato-palmate inequi-anchorate reten- 

 tive spiculum from one of the rosette-shaped groups 

 of those spicula from the dermal membrane. None of 

 the rosette-shaped groups were in a sufficiently perfect 

 condition to render it desirable to figure them. X 

 425 linear. 



Fig. 10. One of the dispersed bidentate, inequi- 

 anchorate, retentive spicula from the dermal mem- 

 brane. X 425 linear. 



Fig. 11. A contort, bihamate, retentive spiculum 

 from the dermal membrane. X 425 linear. 



Fig. 12. One of the subfusiform acuate skeleton 

 spicula. X 264 linear." 



