148 PLATE LVIII. 



Bpicula varies to some extent in the form of its develop- 

 ment. Fig. 150, Plate VI, in vol. i of this work, 

 represents one of these spicula in which the character 

 of the fimbriation is somewhat different to that of fig. 

 12 in the present plate ; both are from the same sponge. 

 X 660. 



Fig. 13. — A small, tridentate, equi-anchorate, reten- 

 tive spicnlum from the dermal membrane, without any 

 trace of fimbriation. X 530 linear. 



Fig. 14. — An entirely but incipiently-spined 

 skeleton sjjiculum. X 250 hnear. 



IsoDiCTTA Bdwakdii, Bowerhanh. 



Vol. ii, p. 325, ' Mon. Brit. Spongiada;.' 



Fig. 15. — Represents the type-specimen of the 

 sponge in the cabinet of the Rev. A. M. Norman. 

 Natural size. 



Fig. 16. — One of the long and slender acuate tension 

 spicula from the dermal membrane. X 250 linear. 



Fig. 17. — A bidentate, equi-anchorate, retentive 

 spiculum from the dermal membrane. X 530 hnear. 



Fig. 18. — One of the skeleton spicula. X 250 

 linear. 



IsoDiCTTA LOBATA, Boiverhank. 



Vol. ii, p. 326, ' Mon. Brit. Spongiadfe.' 



Fig. 19. — Represents the specimen of the species I 

 received from Mrs. Grithths. Natural size. 



Fig. 20. — A slcuflor, acuate, tension spiculum from 

 the dermal membrane. X 250 linear. 



Fig. 21. — One of the skeleton spicula. X 250 

 linear. 



Fig. 22. — An inequi-dentato-palmate, retentive 

 spiculum from the interstitial membranes. X 530 

 linear. 



