PLATE II. 



Geantia tesseli,ata, Boiverbanlc. 



Vol. ii, p. 26, ' Mon. Brit. Spongiadae.' 



Figs. 21, 22. — Represent two specimens of G. 

 tessellata based on fragments of shells. Natural size. 



Fig. 23. — Represents a longitudinal section of O. 

 tessellata exhibiting the compact disposition of the cells 

 of the skeleton and the leno-th and form of the cloacal 

 cavity. Natural size. 



Fig. 24. — A YJew of the external surface of the cor- 

 responding half of the sponge represented by fig. 23. 

 Natural size. 



Fig. 25. — A magnified view of a portion of the 

 internal surface of the specimen represented by fig. 23, 

 exhibiting a jDortion of tlie oscular areas opening into 

 the cloaca at (a) ; the form, structure, and arrange- 

 ment of the cells of the skeleton, and the compact 

 (iorymbose bundles of small acerate defensive spicula of 

 the external surface of the sponge. X 50 linear. 



Fig. 26.- — A magnified view of a portion of the 

 external surface of the specimen represented by fig. 

 24, exhibiting the tessellated appearance produced by 

 the compact disposition of the corymbose bundles of 

 the minute acerate external defensive spicula. X 80 

 linear. 



Fig. 27. — One of the stout equiangular triradiate 

 spicula of the skeleton. X 123 linear. 



In vol. i, Plate XVII, fig. 286, ' Mon. Brit. Spon- 

 giadse,' there is represented a portion of the inner sur- 

 face of the cloaca of 0- tesseUcda, showing the form and 

 mode of disposition of the ensiform, spiculated, equi- 

 angular, triradiate, internal, defensive spicula, and their 

 curvature towards the mouth of the cloaca. X 108 

 linear. 



