138 A MONOGRAPH OF THE 



the length of an average size of skeleton spiculum, about 

 half a line. 



The skeleton spicula occasionally, although rarely, attain 

 the length of a line, and this extension of the ordinary 

 length usually obtains when the skeleton column is repre- 

 sented by a single spiculum, which has its base in the 

 basal membrane and its apex projected through the der- 

 mal one. 



There is a paucity of keratode, and an immaturity in 

 the production of the skeleton columns, which appears to 

 indicate a young condition of the sponge ; this is assuredly 

 the case hi the marginal portions, and notwithstanding the 

 large area of its surface I am strongly inclined to believe 

 that no part of it is in a fully developed condition, and 

 that hereafter, in older specimens, the skeleton columns 

 will be found in a much more satisfactory state of de- 

 velopment. 



8. MicRocioNA ATRASANQUiNEA, Bowerbauk. 



Sponge. Coating thin , surface minutely hispid. Oscula 

 simple, minute, numerous. Pores inconspicuous. 

 Dermal membrane pellucid, thin, spiculous; tension 

 spicula acuate or sub-clavate, long and slender, and a 

 few tricurvato-acerate ; retentive spicula bidentatei, 

 equi-anchorate, few in number. Skeleton columns 

 short and stout ; spicula of the body of the column 

 fusiformi-attenuato-sub-spinulate, short and rather 

 stout ; of the terminations long and^ large, curved 

 outwardly, projected through the dermal membrane 

 for half or two thirds their length, as external de- 

 fences. Internal defensive spicula sub-spinulo-acuate; 

 entirely spined, few in number. Interstitial mem- 

 branes rare ; spicula same as those of dermal mem- 

 brane, few in number. 



Colour. — Alive, dark blood-red ; dried, brown or dirty 

 green. 



