PLATE XI. 



"MioEooiONA TUMULOSA, Bowerlank. 



Kgs. 1, 2. — Represent the type-specimens of tlie 

 species. Natural size. 



Fig. 3. — A small portion of the skeleton structure 

 of the sponge exhibiting the irregular mode of the 

 disposition of the slender, compact, skeleton columns 

 and the interstitial spicula dispersed amid them. 

 X 94 linear. 



Fig. 4. — One of the skeleton spicula. X 264 linear." 



" IsoDiCTYA TETJNCA, Bowerhank. 



Fig. 5. — The type-specimen of the species. Natural 

 size. 



Fig. 6. — A specimen of the species exhibiting a 

 considerable variation in form. Natural size. 



Fig. 7. — One of the slender, acerate, dermal tension 

 spicula. X 666 linear. 



Fig. 8. — A subfusiformi-acerate, skeleton spiculum. 

 X 666 linear. 



Figs. 9, 10. — Two of the attenuato-acuate, internal, 

 defensive spicula, exhibiting the variations in form and 

 basal spination of their truncated bases. X 1166 

 linear." 



