12 A MONOGRAPH OF THE AUSTRALIAN SPONGES, 



The surface is shining as in other species, but not quite smooth. 

 A reticulate structure as described by O. Schmidt (1) of Chon- 

 drosia plebeja does not exactly ruake its appearance, but still the 

 roughness is of a kind not met with in other species of Chondrosia, 

 so that by this alone our species is distinguished from others. 



A transverse section shows, that the cortex is highly developed, 

 and has a dark outer margin, it is very light coloured towards the 

 interior. The Pulpa is of a uniform daik brown color. A few 

 canals are seen in it (fig. 6), but these are rare and small, so that 

 the Sponge is pretty dense, as is the rule with the genus. 



The Osculae are more numerous than in other species, and 

 grouped together asin Osculina (2). They possess small " chimneys" 

 that is thin membraneous frills about 1 mm. high, which however 

 are simple cylindrical, and have a siiiooth margin (different from 

 Osculina.) 



The Canal System. 



The Canal System certainly shows some peculiarities which 

 distinguish it fiom the hitherto investigated species, and if I 

 have not established a new genus for our Sponge I have not 

 done so mainly for the sake of simplicity and also because 

 the canal system of our species although peculiar can be easily 

 derived from that, so excellently described, of Chondrosina reni- 

 formis by F. E. Schulze (^3). 



Scattered all over the surface we find small pores, measuring 

 about 0-01 across. These are circular and we soon perceive that 

 they are always situated in groups of 5 — 10 and in fact, that there 

 always lies a group of such pores at the base of an indenture. 

 These indentui-es of the surface are inconspicuous. Their existence 

 causes the roughness of the surface described above (fig. 8). I 

 think it highly probable, that the pores of Chondrosia plebeja may 

 be distributed in a similar manner, 



(1) 0. Schmidt. Die Spongien der Kiiste von Algier. Seite 1. 



(2) O. Schmidt L.c. Seite 2. 



(3) F. E. Schulze. Die Familie der Chondrosidae. Zeitschrift fiir 

 wissenschaftliche Zoologie. Band XXIX. Seite 100 flf. 



