OF THE SPONGIAD^. 343 



SPICULA OP THE MEMBRANES. 



TENSION SPIOUIiA. 

 Fre. 



90. FUSIFOBMI-ACERATE : ENTIREJiT SPJNED. X 660 



linear. — This forn^ pf spiculurp. occurs abundantly 

 in the dermal and interstitial membranes of Span- 

 gilla lacmtris^ Johnston. Paiges 38, 43, and 58. 



91. FuSirOBMJ-ACEBATE : TRTTNCATEDLY SPINOUS, X 660 



linear. — Abundant in Sjpotiffill^ alkg,. Carter, in 

 both the dermal and interstitial piembranes. Page 



42. 



92. MucRONATO - CTLiNDRicAL. X 400 limear. — ^The 



dermal membrane of Hedichondria incntstans, 

 Johnston, is abundantly furnished with large fiat 

 fasciculi of this form of spiculum. They are as 

 long as those of the skeleton, but not above half 

 their diameter ; they are entirely destitute of spines, 

 while the spicula of the skeleton are covered with 

 those organs. Page 40. 



— . Terminally spined suBFUsiro?,Mi-CYLiNDRicAL. — 

 This form of spiculum is abuijdant in the dermal 

 membrane of Hedichondria nigricans, Bowerbank, 

 where it occurs in irregular fasciculi. It is as long 

 as the spicula of the skeleton, but has not quite 

 so great a diameter, ^nd is distinctly diflBbrent in 

 its form. 



93. Tuberodlated edsiformi-cylindirical. X 660 



linear. — These mijiute ^piciila are profusely dis- 

 persed on the inner ^iirface of the dernjal ^ijd inter- 

 stitial ipembranes pf Pmhym^i^t^ff JoTinstonia, 

 Bowerbg-nk. They are covered very irregularly 

 with il}-defined tijbeyples. They vary very con- 

 siderably in fprm and proportion^. TJ^eir average 

 dimensions are, length gi^th inch, diameter s^th 

 inch, Page 42. 



