188 BRITISH SPONGES: 



bank allows me to add the following fuller and more accurate 



one : — 



" Form massive, variable, sessile ; surface exasperated, of a 



dull ochreous colour. Excurrent canals few, large ; fibres of the 



skeleton rigid, coarsely reticulated, rugose, with numerous 

 grains of sand imbedded in their substance ; or tubular with 

 few or no grains of sand imbedded ; spicula of the skeleton va- 

 riable in size and form, imbedded within, or attached to the 

 outer surface of the pore. 



" The form of this species is exceedingly variable. In its 

 young state, it is spread over the surface to which it is at- 

 tached, as if it were a coating sponge, but when fully de- 

 veloped, it rises to the height of two or three inches, and has 

 a tendency to assume a thickened fan shape, or compressed 

 form ; and the base is usually twice or thrice as long as it 

 is broad, as if this were the natural mode of its develope- 

 ment. It is of a dull yellow ochreous colour, and has the 

 surface much aspirated by the projection of numerous stout 

 sandy fibres. The excurrent canals are large and few in num- 

 ber, and have their terminations occasionally projected beyond 

 the surface. The fibre of this species varies considerably in its 

 character. The larger and coarser portion is constinicted of 

 grains of sand of various sizes, encysted separately in the sub- 

 stance of the horny structure. Among the arenaceous fibres there 

 are others of a fistulose structure, which have few or no grains 

 of sand imbedded in them. In the largest of the arenaceous 

 fibres, the grains of sand are accumulated in such numbers, and 

 so closely built together, as frequently to render the fibre nearly 

 impervious to light ; but in the smaller ones, they are few in 

 number, and disposed in nearly the centre of the fibre. A few 

 spicula are occasionally found imbedded among the grains of 

 sand, or attached to the surface of the fibre. The tubular 

 fibres are smaller than the arenaceous ones, but originate from 



