285 



PLATE LXXXV. 



ISODICTYA FILAMENTA, BowerhccnJc. 



Fig. 1. — Represents tlie sponge, mounted in Canada 

 balsam. Natural size. 



Fig. 2. — A portion of tlie sponge at about (a figure 

 1) X 80 linear. 



Fig. 3. — One of tlie slender acerate spicula from the 

 dermal membrane. X 250 linear. 



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

 X 250 linear. 



IsoDiCTYA LUTEOSA, BowerbanJc. 



Fig. 5. — Represents the type-specimen of the species. 

 Natural size. 



Fig. 6. — One of the skeleton spicula. X 250 

 linear. 



Fig. 7. — A tension spiculum from the interstitial 

 membrane. X 250 linear. 



IsoDicTyA iNVALiDA, Bowerhank. 



Fig. 8. — Represents the type-specimen. Natural 

 size. 



Fig. 9. — An average-sized skeleton spiculum. X 250 

 linear. These spicula vary considerably in their 

 length. 



Fio'. 10. — An acerate spiculum from the skeleton. 

 X 250 linear. This form of spiculum occurs very 

 rarely among the normal acuate ones. 



