APPENDIX. 233 



B. THE GENUS CLTONA. 



In 1826 Robert Grant established a genus Cliona for 

 a sponge which he found perforating the oysters of 

 the Firth of Forth, and thirteen years afterwards a 

 genus to receive the same perforating sponges was 

 named by Nardo Vioa. In 1849 and 1867 my friend, 

 Mr. Albany Hancock, described many species referable 

 to this genus, and most clearly demonstrated that the 

 perforations occupied by the sponge were excavated by 

 the sponge itself. Dr. Bowerbank, however, per- 

 sistently refused to entertain any other opinion than 

 that these sponges always occupied previously-formed 

 excavations and had no power of penetrating shell or 

 stone themselves; nor would he acknowledge the species 

 which had been so carefully described by Mr. Haicock, 

 but united the whole of them under the sponge which 

 he called Hymeniacidon celatus. The following ire the 

 species of Hancock : 



1. CLIONA CELATA (Grant], 



C. celata, Hancock. Ann. Nat. Hist., ser. 2, vol. iii (l|49j, p. 



332 ; and ser. 3, vol. xix (1867), p. 3 (separate copy). 

 Hymeniacidon celatus, Bowerbank. 



Sponge clear, yellow ochre colour. Spicules cf one 

 form only, spinulate, sometimes slightly fusiform: but 

 generally gradually tapering, very long, y^jth o; an 

 inch ; head well defined, globular, approaching oiate, 

 with generally a terminal point. 



Common in oyster shells, Firth of Forth, &c. 



