GEODIA. 27 



ORDER II. SILIOEA, i, 166; n, 3. 

 SUBORDER I. i, 166; n, 3. 



Genus 5. GEODIA, Lamarck, i, 167 ; n, 3. 



GEODIA ZETLANDICA, Johnston, u, 45 ; in, PI. VII, 

 figs. 110. 



1867 Oydoniwn Mulleri, Gray. Proc. Zool. Soc., p. 548. 

 1870 Geodia Zetlandica, Scliraidt. Grunzitge einer Spongien 

 des Atlantisclien Gebietes, p. 76. 



Carter has described three forms of Geodia from the 

 " Porcupine" dredgings, but does not record G. Zet- 

 landica as having been met with in that expedition. 

 His Geodia megastrella, however, appears to come very 

 near to Johnston's species. May it not be the same ? 

 The chief difference appears to be that G. Zetlandica is 

 described by Bowerbank as having not only fusiformi- 

 acerate skeleton spicula, but also " fusiformi-acuates" 

 while the latter do not occur in G. megastrella. It is, 

 however, worthy of notice, that although these spicula 

 are described in Vol. II, no figure is given of them in 

 Vol. Ill; did our author find that he had made a 

 mistake with respect to these spicules ? But granted 

 the presence of fusiformi-acuates along with the fusi- 

 formi-acerates of G. Zetlandica, and their absence in 

 G. megastrella, would this character be necessarily of 

 specific importance in this group of sponge ? If the 

 reader will turn a few pages on to the description of 



