118 Mr. H. J. Carter on 



this spicule shows that the pin-like form alone cannot be 

 considered " monactinellid " (one-rayed) any more than the 

 simple acerate, which consists of two rays growing in oppo- 

 site directions from the central cell. " Diactinellid " would 

 etyraologically suit this form best (two-rayed) . 



19. Suherites insignis. 



Massive, sessile, depressed, elliptical, slightly convex, trun- 

 cated below; covered with warty tubercles at one end and 

 with large thin-mouthed vents at the other, each in juxta- 

 position, with a smooth space in the centre between them, 

 altogether looking very much like a large sea-slug. Con- 

 sistence firm, tough. Colour when fresh " dark slate-grey," 

 now much the same, with a tinge of violet-red. Suiface 

 smooth, dermis thin. Vents congregated chiefly over one 

 end. Spicules of one form only, viz. pin-like ; head varying 

 from subglobular to simple acuate, 100 by l^-6000th in. 

 more or less. Internal structure cavernous, tissue compact. 

 Size 1| in. high by 4 x 2^ horizontally. 



Depth 19 fat h. 



Ohs. This is a very remarkable sponge on account of its 

 structure, which consists chiefly of enormously dilated 

 excretory canals, into which the water &c. entering through 

 the pores and their subdermal cavities is received and dis- 

 charged by the vents ; while the surface of the excretory 

 canals as usual presents the characteristic subcircular rugaj 

 together with the apertures of small canals between them. 

 Passing from the surface inwards the dermis may be ob- 

 served to be composed of a finely reticulated structure, in 

 each interstice of which are several pores whose apertures 

 lead into the subjacent subdermal cavities, which together 

 form a layer that is continued over the warty tubercles as 

 well as over every other part of the surface, forming in 

 many parts the outer wall or roof of the great dilated excretory 

 canals, which thus receive the contents of the subdermal 

 cavities through holes corresponding to the pores externally, 

 and finally eject them, or such parts as are not necessary for 

 the nourishment of the sponge, through the large thin- 

 mouthed vents at the other end of the specimen, thusaftbrding 

 another instance of a direct communication between the pore 

 and excretory canal systems. The " cavernous " structure 

 seems to find an analogue in the similarly-dilated canal-struc- 

 ture (lacunar) of Chondrosia reniformis^ Nardo, and C Ram- 

 sayi, Von Lendenfeld (Proc. Linn. Soc. N. S. Wales, vol. x. 

 pt. 1, p. 147, pi. iii ), of which there are two or more speci- 

 mens in Mr. Wilson's collection from " Western Port." 



