13 



PLATE VI. 



Leuconia pumila, Boiverhank. 



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



Figs. 1, 2, 3. — Leiiconla immila. Natural size. 



Fig. 4 represents a portion of tlie surface of a 

 specimen of Leuconia purnilo, exliibiting the great 

 yariety in the size of the skeleton spicula, the space 

 between the extreme points of the largest triradiate 

 spiculum Ijeing very little short of that of the diameter 

 of the sponge. X 80 linear. 



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

 j9iwr«7a representing a space extending from the external 

 surface of the sj^onge to the surface of the cloacal 

 cavity, and the mode of the disposition of the skeleton 

 spicula (ft) being the external surface. X 80 hnear. 



Lbuoogtpsia Gossei, Boiverhank. 



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



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- 

 formi-acerate spicula, disposed at various angles to the 

 surface. X 60 linear. 



Fig. 6, vol. iii. — One of the large fusiformi-acerate 

 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. 



