HALICHONDRIA. 109 



The dermal membrane is especially characteristic of 

 the species. It is abundantly supplied with spicula ; 

 the tension ones are subfusiformi-cyliudrical, rather 

 long and slender ; on some parts of the membrane 

 they are dispersed indiscriminately, but most frequently 

 they are more or less gathered into broad, flat fasciculi, 

 many of which radiate at one extremity in a fan- 

 shaped manner. The retentive spicula are also very 

 numerous. The simple and contort bihamates are 

 small, and some of them very minute ; they vary in 

 length from y-J-g- inch to ^QQ inch, while the length 

 of the fully developed bidentate, auchorate spicula, 

 average 8 -|- 2 - inch in length. This near approxima- 

 tion of the fully developed anchorate and bihamate 

 spicula in their length is very unusual, as it is most 

 frequently the case that the latter form is at least 

 twice as long as the former. The bidentate equian- 

 chorate spicula are also numerous ; comparatively 

 speaking they are stout and well developed in their 

 mature state, but in this specimen they may be seen 

 in various early and progressive stages of development 

 in the form of minute simple bihamate spicula, very 

 different in their shapes from the real bihamate ones. 



The skeleton is very irregular in its structure, but 

 decidedly reticulate. The rete is also more or less 

 irregular ; in some parts it is multispiculous, while in 

 others it is constructed of only two or three spicula. 

 The spicula of which it is formed are very much larger 

 than those of any other part of the sponge ; they are 

 decidedly fusiform, and occasionally subclavate at the 

 base. The interstitial membranes are abundantly 

 supplied with both forms of the retentive spicula, but 

 the tension forms, so abundant on the dermal membrane, 



