106 A MONOGRAPH OF THE 



which are all more or less furcate. All the branches are 

 compressed, and they occupy nearly the same plane. The 

 hispidation is strikingly characteristic in this sponge ; the 

 whole surface is furnished with numerous radiating fasciculi 

 of large and long acuate spicula ; each group contains from 

 six to about ten spicula, diverging from each other at small 

 angles, so that the whole combined present a regular series 

 of defensive points at a slight distance beyond the dermal 

 surface, while the bases of the groups are widely and dis- 

 tinctly separated from each other ; the spicula are stouter 

 and stronger than those of the skeleton. The axial column 

 of the sponge is comparatively large ; it extends very nearly 

 to the dermal membrane. The skeleton spicula, acerate 

 and acuate, are indiscriminately mixed in the structure, 

 both are long and slender in proportion to their diameter, 

 the acerate rather preponderating in number. 



From its size, form, and general aspect, this species may 

 readily be confounded with D. stuposa by a hasty observer, 

 but the total absence of stellate spicula in the dermal mem- 

 brane distinguishes it at once from that species. The 

 general habit of D. fascicularis, imd the species under 

 consideration, are so like each other that those who are not 

 acquainted with both species might be apt to confound the 

 two, by the description of the external characters only, but 

 here, again, a microscopical examination of either species 

 will quickly relieve us from this chance of error. 



4. Dictyocylindrus Howsei, Bowerbank. 



Sponge. Arborescent, pedicelled ; branching dichotomously 

 or trichotomously ; branches slightly compressed, his- 

 pid ascendingly, surface smooth (?). Oscula and pores 

 inconspicuous. Dermal membrane pellucid, aspicu- 

 lous. Skeleton. Spicula sub-fusiformi-acuate, often 

 sub-spinulate, large. External defensive spicula same 

 as those of skeleton, large and long. Tension spi- 

 cula abundant. Acuate, rarely acerate, slender, and 

 often flexuous ; disposed in irregular, broad fasciculi. 



