114 A MONOGRAPH OF THE 



them exceed a line in diameter at the base, and they gra- 

 dually attenuate to their distal terminations. When held 

 up to the light they appear profusely spinous, the spi- 

 cula projecting at right angles to the surface, frequently to 

 the extent of two or three times the diameter of the part of 

 the branch whence they spring. The branches all attain 

 to nearly the same height, and their terminations are fur- 

 nished with numerous large defensive spicula, which are 

 projected in lines nearly in accordance with the axis of the 

 branch. 



From the appearance of the dried specimens it is pro- 

 bable that in the living condition the diameter of the 

 branches would be at least twice that of their present con- 

 dition. The secondary external defensive system consists 

 of numerous fasciculi of comparatively small, slender, 

 acutely terminated spicula, diverging from the base of the 

 fasciculus, and spreading in every possible direction. The 

 internal defensive spicula are very numerous, and are ex- 

 ceedingly various in size. Many of them are abruptly 

 curved near the base, and the clavate expansion at the base 

 of the greater portion of them is excentric to the axis of 

 the spiculum. 



9. Dictyocylindrus pumilus, Bowerbank. 



Sponge. Sessile, or very slightly elevated on a massive 

 pedicle ; branching dichotomously or trichotomously ; 

 branches short, stout, obtusely terminated. Surface 

 very slightly hispid in the living state. Oscula 

 simple, dispersed. Pores inconspicuous. Dermal 

 membrane pellucid, aspiculous. Skeleton : spicula 

 of axis sub-spinulate or acuate, rarely enormi-spinu- 

 late ; radial spicula same as those of the axis. In- 

 ternal defensive spicula attenuato-acuate or sub- 

 spinulate, entirely spined. Tension spicula acuate or 

 acerate, long and slender. 



Colour. Alive, dark gray, with a tint of green. 



