151 



PLATE LIX. 



Spongilla FLuviATiLis, Johuston. 



Vol, ii, p. 339, ' Mon. Brit. Spongiadaj.' 



Fig. 1. — Represents a specimen from tlie floating 

 timber in the West Country Dock, near Rotlierhithe, 

 London, S.B. The surface has assumed a somewhat 

 fohated appearance. Natural size. 



Fig. 2. — A specimen from the same locality as that 

 represented by fig. 1. The upper and the lower por- 

 tions have been two distinct specimens which have 

 united by approximation. This specimen, represents 

 the usual massive character of the species. Natural 

 size. 



Fig. 3. — Represents an average-sized skeleton spi- 

 culum. X 260 linear. 



Plate XXII, fig. 317, vol. i, ' Mon. Brit. Spongiada3,' 

 rej^resents an ovarium of this species in its natural 

 state, exhibiting the foramen. X 83 linear. 



Fig. 318.- — Represents a perfect skeleton of one of 

 the ovaries, prepared with nitric acid. X 183 linear. 



Fig. 319. — Exhibits a section at right angles to the 

 surface of a fragment of the skeleton of one of the 

 ovaries, prepared by nitric acid, showing the relative 

 positions of the rotulate spicula in the ovarium ; (a) a 

 detached spiculum from the same specimen. X 308 

 linear. 



Plate IX, fig. 217, in the same volume, represents 

 one of the rotulas irregularly and deeply dentate. X 

 660 linear ; fig. 218 in the same plate is a view of the 

 external surface of one of the rotul^. X 660 linear. 



