302 a monograph op the australian sponges, 



Shape and Size. 



Halme simplex is a low, incrusting sponge. The crusts are 

 higher in the centre than at the margin and of irregular roundish 

 outline. The regularity of the outline is often disturbed and then 

 we find lobate extensions of varying shape and size. The crust 

 has a thickness of 12-20 mm., and may extend to 100 mm. (the 

 largest specimen seen by me). 



Color. 



The sponge is generally, alive and also when dry, of a uniform 

 dark chesnvit color, I have however seen some dried, badly 

 preserved specimens of it, which were grey. 



Structure. 



Thesponge consists of lamelloe which are not nearly so complicated 

 in their plications as those of the foregoing species. The honeycomb 

 structure (Plate XXVI., fig. 3) is more simple than in Halme 

 nidus vesparum. The whole of the lamella appears as a portion of 

 an irregular comb. The surfaces are curved in one direction 

 (laterally) only, whereas they are straight in the other direction 

 (vertically). From a basal incrusting lamella numerous upright 

 and much curved septa or lamelke arise between which there are 

 large conic spaces (Plate XXVII., fig. 6). These lamellse corres- 

 pond to the interior lamellse of the foregoing species. The conic 

 spaces between them are the vestibule lacunae. An external 

 lamella as described above is not met with ; the conic lacunse are 

 in open communication with the sea-water outside. 



The skeleton is similar to that of Halme Nidus Vesparum and a 

 cortical layer of sand grains is met with. This latter consists of a 

 thick layer of lai-ge grains on the free margins of the lamellse and 

 of a thin layer of small grains further down in the surface near 

 the bottom of the conic spaces. Half way up we find a cortex 

 intermediate between the two. 



It appeared to me that the skeleton in general was more coarse 

 than in the other species, microscopic measurements, however, 



