PLATE I. 



" HYMEDESMIA PANSA, Bowerbank. 



Fig. 1. A small portion of the sponge, exhibiting 

 the mode of fasciculation and disposition of the skele- 

 ton fasciculi. X 250 linear. 



Fig. 2. One of the long, slender, acuate spicula of 

 the skeleton fasciculi. X 420 linear. 



Fig. 3. Represents one of the attenuate -acuate, 

 entirely spined defensive spicula. X 420 linear. 



Fig. 4. One of the bidentate, equi-anchorate, re- 

 tentive spicula. X 420 linear." 



" HYMEDESMIA TENUICULA, BowerbanJc. 



Fig. 5. Represents a portion of the flat fasciculi 

 composed of numerous attenuate- spinulate spicula, 

 and the irregular mode of their disposition. X 150 

 linear. 



Both the species figured above depend for their 

 identification on their microscopical structures alone; 

 figures of their extremely thin substances would not 

 contribute in the slightest degree to their identifica- 

 tion." 



