ADDITIONS AND CORRECTIONS. 197 



gibberosa of Lamarck, (Anim. s. \'ert. 2de edit. ii. 394,) and 

 of Blainville ; (Man. d'Actinol. 535, pi. 91, fig, 4,) and is said 

 to be a native of the shores of Guinea. 



Halichondria saburrata, p. 120. 

 From an inadvertency, which I cannot explain, the spicula 

 of this sponge have been described as " short, curved and 

 double-pointed." They are, on the contrary, short, obtuse at 

 one end, and pointed at the other, and in fact are so like those 

 of Halichondria inci'ustans as, perhaps, to prove that H. sa- 

 burrata mav be reckoned a mere variety of that species. 



Halichondria areolata, p. 121. 

 I suspect that this is a crustaceous state o^ Diiseideia fragi- 

 lis. An examination of a specimen of the latter in a fresh 

 condition, given me by Mr Bowerbank, has forced this convic- 

 tion upon me. 



Halichondria seriata, p. 125. 

 The spicula are considerably shorter than those of H. in- 

 crustans, rather thick, more or less curved and awl-shaped. 

 The one end is obtuse, the middle bulges a little, and thence 

 the spiculum tapers to a point. The membrane that mvests the 

 central cavity of the spiculum is very obvious in this species. 



Halichondria celata, p. 125. 

 Mr William Thompson lately sent me an old and much worm- 

 eaten oyster shell marked, on the inner surface, with a circular 

 white flocculent or spongy incrustation which, on a microsco- 

 pical examination, proved unexpectedly to be a state of H. ce- 

 lata. It had no connection with the perforations in the shell ; 

 and no resemblance to the sponge in its normal state. 



Halichondria virgultosa, p. 137. 

 When entire, the spicula appear mostly to have a small head, 

 and to be shaped like a slender pin. 



Halichondria suberea, p. 139. 

 On examining the spicula anew, with a better microscope 



