1100 A MONOGRAPH OF THE AUSTRALIAN SPONGES, 



19. SPECIES. UTE ARGENTEA. Pol(^jaeff (1.) 



The Sponge has the shape of an elongated tuV)e, 40 mm. lonjj; 

 and 3 mm. thick. (The only specimen.) Bodywall 0-5 mm. thick. 

 Half of its thickness is taken up by the strong cortex. Outer 

 surface smooth. 



Skeleton of the gastric surface : This consists of an outer layer 

 of quadriradiate, of an inner layer of quadriradiate or triradiate, 

 and of minute acerate spicules, scattered amongst those just 

 mentioned without any regular oi'der. 



Obiter quadriradiate Spicules : Basal and lateral rays straight, 

 sharply or rather bluntly pointed, all of the same diameter, 

 0-0 1 mm., and usually of the same length (0-2 5 mm. on an 

 average) ; basal ray forming with each of lateral rays an angle of 

 115* ; apical ray curved tapering from the base to a sharp point, 

 reaching 0-15 mm. in length with a diameter of O'Ol. 



Inner quadriradiate Spicules : Basal ray straight, tapering 

 from base to sharp point, usually rather thinner than lateral rays, 

 forming with each of them an angle of about 100°, length 

 inconstant, varying from 0*1 8 mm. to 0-5 mm. ; lateral rays curved 

 inwards, tapering from the base to sharp points, reaching 0*3 mm. 

 in length, 0*0125 mm. in diameter; most of them ai'e truly 

 quadriradiate, their apical ray being occasionally longer, 0-2 mm., 

 than that of the outer quadriradiate spicules ; its length is, how- 

 ever, varirible, and there are amongst the inner quadriradiate 

 spicules others with a merely incipient apical ray, and even 

 quite deprived of it. 



Minute acerate Spicules : Straight or slightly curved, spindle- 

 shaped, tapering from the centre to a sharp point at either 

 extremity, usuall}' 0*1 mm. long 0-002 mm. in diameter. 



Skeleton of the radial tubes : The tubar skeleton consists of sub- 

 gastric triradiate spicules, reaching with their centrifugally 



(1.) N. PoUjaef. Report on the Calcarea. The Zoology of the Voyage 

 of H.M.S. Challenger. Part XXIV., p. 43, pi. I., fig. 3 ; pi. IV., fig. 3 ; 

 pi. v., fig. la-lp. 



