PLATE XIII. 



" IsoDiOTYA PERTENUis. Bowerhanli. 



Figs. 1, 2, 3. — Represent the type-specimens of tlie 

 species. Natural size. 



Fig. 4. — One of the slender, acuate spicula of tlie 

 skeleton. X 425 linear." 



" Hymedesmia Peachii, Bowerhanh. 



Fig. 5. — Represents the small, angular, dark- 

 coloured stone, the white surfaces on which represent 

 the sponge. Natural size. 



Fig. 6. — The fragment of a bivalve shell, the inner 

 surface of which is nearly covered by the sponge. 

 Natural size. 



Fig. 7. — A small portion of the sponge from off the 

 little angular stone, exhibiting the mode of the dis- 

 tribution of the skeleton fasciculi and the retentive 

 and large auxiliary skeleton spicula. X 264 linear. 



Fig. 8. — One of the slender skeleton spicula from a 

 fasciculus. X 264 linear. 



Fig. 9. — A large attenuato-acuate, basally spinous, 

 auxiliary skeleton. X 264 linear. 



Fig. 10. — An internal, defensive, attenuato-acuate, 

 entirely spined spiculum. X 264 linear. 



Fig. 11. — One of the small, bidentate, equi-ancho- 

 rate, retentive spicula. X 425 linear. 



Fig. 12. — A large, tridentate, retentive spiculum, 

 highly magnified to distinctly exhibit the slender 

 central tooth at each termination. X 666 Linear." 



