350 A MONOGRAPH OF THE 



brane has been destroyed, and the present surface is rugged 

 and very open. Under these circumstances the oscula are 

 not readily detected, and they do not appear to have been 

 either large or numerous, although the surface is thus 

 dilapidated ; in the patches of dermal membrane which 

 remain the characteristic spicula are in situ and in a fine 

 state of preservation, but it is in the interstitial membranes, 

 which are in excellent condition, that the tension and re- 

 tentive spicula arc to be seen in their natural state. The 

 tension spicula are thickly felted together on its surface ; 

 they are very minute and slender, and their length is fre- 

 quently not more than a third or a fourth of that of one of 

 the bihamate retentive spicula. Among the short slender 

 tension spicida there are frequently other acerate spicula of 

 three or four times their length, and these are still more 

 slender than the shorter ones. The retentive spicula are 

 slender but much expanded, and their form is exceedingly 

 variable and frequently distorted, and some of them are of 

 greatly increased strength in the shaft. The greater 

 portion of them are irregularly dispersed among the tension 

 spicula, but occasionally they are found congregated in 

 fasciculi, and in this state their curves are conformable. 



I have dedicated this interesting species to my friend 

 Mr. Peach, whose ardour and ability in the pursuit of 

 natural history is so well and so favorably known to 

 naturalists, and to whose kindness and generosity I am in- 

 debted for this and many other new and valuable speci- 

 mens described in this work. 



4. Desmacidon constrictus, Boicerbanh. 



Sponge. Sessile, fan-shaped (!) Surface, Oscula, and Pores 

 unknown. Dermal membrane aspiculous ? Skeleton, 

 Stout and open ; spicula sub-fusiformi-acuate, con- 

 stricted near the base, long and large. Interstitial 

 membranes sparingly spiculous. Tension spicula very 

 minute acerate or acuate ; retentive spicula, simple and 

 contort bihamate very minute. 



