354 A MONOGRAPH OF THE 



by the Rev. Mr. Norman at Herm between tide marks, 

 was thinly spread over its surface, covering all its inequali- 

 ties, without exhibiting any disposition to rise from the 

 surface on which it reposes ; in this state the skeleton does 

 not resemble those of the allied species of the genus ; the 

 fibres do not exhibit a disposition to anastomose and form 

 an irregular reticulated tissue, as in those sponges ; they 

 originate from the basal membrane in a remarkable manner ; 

 springing from the centre of a radiating group of spicula, 

 and frequently gradually attenuating and terminating 

 acutely without anastomosing with any of the neighbouring 

 fibres, but when they happen to meet they unite. The 

 spin ulation of the skeleton spicula is frequently very slightly 

 produced, and in some cases they might almost be termed 

 acuate, but there is always more or less inflation of the 

 base, especially in the immature spicula. In this condition, 

 and compared with the well-developed specimens of the 

 same species, this sponge might readily be mistaken for a 

 distinct species. 



Raphyrus, Bowerbank. 

 1. Raphyrus Griffithsii, BowerbanTc. 



Halichondria celata, Johnston. 



Sponge. Sessile, massive; surface even. Oscula simple, 

 dispersed, very numerous. Pores inconspicuous. 

 Dermis coriaceous, stout, crowded with spicula ; 

 spicula acuate and spinulate, slender, very vari- 

 able in form. Skeleton. Fibres very large and 

 strong, irregularly dispersed ; spicula subfusiformi- 

 spinulate, and rarely, acuate ; stout. Interstitial mem- 

 branes thick, abundantly spiculous ; spicula subfusi- 

 formi spinulate or acuate, long, and slender. 



