12 PLATE V. 



spicula of the lining membrane of the cloaca. X 130 

 linear. 



Leuconia fistulosa, Boiverbank. 



Vol. ii, p. 39, 'Mon. Brit. SpongiadES.' 



Fig. 9. — A specimen of L. fistulosa from Plymouth. 

 Natural size. Dried specimen. 



Figs. 10, 11. — Two specimens of L. fistulosa from off 

 Saints' Bay, Guernsey. Xatural size. Dredged by 

 the Rev. A. M. Norman. From dried specimens. 



Fig. 12. — One of tlie large fusiformi-acerate, ex- 

 ternal, defensive spicula. X 80 linear. 



Fig. 13. — An equiangular, triradiate, skeleton spicu- 

 lum of the normal form. X 123 linear. 



Fig. 14. — An equiangular, triradiate, skeleton spicu- 

 lum of an abnormal form. X 123 linear. The elonga- 

 tion of the third ray is variable, and usually in the 

 direction of the long axis of the sponge. 



Fig. 15. — One of the spiculated, equiangular, tri- 

 radiate, internal, defensive spicula. X 123 linear. The 

 spicular ray is in the downward direction. 



Fig. 16. — One of the slender, rectangulated, triradiate 

 spicula. X 123 hnear, from near the mouth of the 

 cloacal cavity. 



