332 PLATE XOI. 



Fig. 12. One of the internal, spiculated, equi- 

 angulated, defensive spicula from the interior of one of 

 the large cloacal fistulas. X 250 linear. 



Fig. 13. An equi-angulated, triradiate, skeleton 

 spiculum of the normal form. X 250 linear. 



Figs. 14, 15. Two examples of the distorted forms 

 of the equi-angulated, triradiate, skeleton spiculum. 

 X 250 linear. 



Fig. 16. One of the rectangulated, triradiate, 

 skeleton spicula in very nearly its normal form. X 250 

 linear. 



Fig. 17. A slightly distorted example of the rectan- 

 gulated, triradiate, skeleton spiculum. X 250 linear. 



HALICHONDRIA MclNTosmi, Bowerbank. 



Fig. 18. Represents the type-specimen. Natural 

 size. 



Fig. 19. An average-sized, acerate, skeleton spicu- 

 lum. X 250 linear. 



DYSIDEA CORIACEA, BowerbanL 



Fig. 20. Represents the type-specimen. Natural 

 size. 



ISODICTYA EUGOSA, Bowerbank. 

 Plate XCI. 



Sponge massive, sessile, parasitical on fuci or 

 zoophytes. Surface uneven, very rugose. Oscula 

 simple, dispersed. Pores inconspicuous. Dermal mem- 

 brane abundantly spiculous ; tension spicula, sub-fusi- 

 formi acerate, disposed in numerous flat fasciculi, or 

 dispersed ; retentive spicula ; bidentate equi-anchorate, 

 very variable in size, rather numerous ; and simple and 

 contort bihamate, very variable in size, numerous. 

 Skeleton. Irregular, primary lines multispiculous, 

 secondary lines rarely more than bi-spiculous ; spicula 



