18 



PLATE VI. 



LEUCONIA PUMILA, Bowerbank. 



Vol. ii, p. 41, ' Mon. Brit. Spongiadse.' 



Figs. 1, 2, 3. Leuconia pumila. Natural size. 



Fig. 4 represents a portion of the surface of a 

 specimen of Leuconia pumila exhibiting the great 

 variety in the size of the skeleton spicula, the space 

 between the extreme points of the largest triradiate 

 spiculum being very little short of that of the diameter 

 of the sponge. X 80 linear. 



Fig. 5. A portion of a longitudinal section of L. 

 pumila representing a space extending from the external 

 surface of the sponge to the surface of the cloacal 

 cavity, and the mode of the disposition of the skeleton 

 spicula (a) being the external surface. X 80 linear. 



LEUCOGYPSIA GOSSEI, Bowerbank. 



Vol. ii, p. 42, ' Mon. Brit. Spongiadse.' 



Vol. ii, plate xxvi, fig. 350, represents a very 

 characteristic specimen of L. Gossei of the natural size. 



Fig. 349, in the same plate, represents a section at 

 right angles to the surface of the sponge, exhibiting 

 the irregular interstitial structure, with the large fusi- 



o o 



formi-acerate spicula, disposed at various angles to the 

 surface. X 50 linear. 



Fip;. 6, vol. iii. One of the large fusiformi-acerate 



O O 



spicula. X 123 linear to show the size as compared 

 with the other spicula of the sponge. 



Fig. 7. One of the equiangulated, triradiate spicula 

 of the skeleton. X 123 linear. 



Fig. 8. A spiculated, equiangulated, triradiate, 

 internal, defensive spiculum. X 123 linear. 



