BY R. VON LENDENFELD, PH.D. 1145 



Oscular Triradiate Spicules. Sagittal, basal ray forming with 

 each lateral ray an angle of 90° ; basal ray straight, 

 tapering from the base to a sharp point, usually half as thick as 

 lateral rays, often still thinner, occasionally almost of the same 

 diameter; length inconstant, rarely more than 05 mm., often 

 not exceeding 0-0 1 mm. or still less; lateral rays either 

 straight or slightly curved inward, usually sharply pointed, ten 

 times as long as thick, average length 0*01 mm. ; connected as 

 regards their form and size with the sagittal subdermal triradiate 

 spicules of the osular surface by a long series of intermediate 

 stages. 



Oscular Quadriradiate S2ncules. Like the rectangular Triradiate 

 nothing but modified sagittal triradiate spicules of the Oscular 

 surface ; lateral rays either straight or slightly curved forwards, 

 tapering from the base to approximately sharp points, average 

 length 2 mm, by 02 mm., basal ray usually rather shorter, 

 straight, sharp pointed, forming with each of the lateral rays an 

 angle of about 110*^ ; apical ray curved, not seldom undulating, 

 sharp-pointed like the facial rays, usually rather thinner than 

 these latter; length varying from 0"06 to 0*2 mm. 



Locality: Station 163a, June 3, 1874, off Port Jackson ; depth, 

 30 to 35 fathoms; rock. Station 163, April 4, 1874; latitude 

 36« 58' S., longitude 150° 30' E. ; depth, 120 fathoms; ofi 

 Twofold Bay, Australia, Challenger. 



EXPLANATION OF PLATES. 



Plates., LIX to LXVII. 



Fig. la. — Ascetta procumbens. R. v. L. Three colonies on a sheU of 

 Mytilus. Natural si:e painted from life. The middle-sponge 

 is young and consists of only a few separate individuals. 

 These tubes soon grow out to form a felt-like texture as seen in 

 the other two Sponges, and leaving round, trumpet-like Pseud 

 oscula between them. (Port Jackson, Laminarion zone.) 



