Sponges fi-om South AvstraUa. 47 



cavity throughout, as before stated ; also in a minute form 

 echinating the interstices of the dermal reticulation, to which 

 it thus imparts an additional hispid character. Size of speci- 

 men about 5-12ths in. long, and 2-12ths in. in its greatest 

 diameter. 



Ohs. This specimen is remarkable for presenting the delicate 

 sarcodic network over the surface of the cloaca which seems 

 to occur occasionally (see Hiickel's representation of Leiicetfxi 

 pandora^ ' Atlas,' Taf. 22. fig. 3 b), sometimes, as in this 

 case, occupying the whole of the cavity with its clathrous 

 structure ; also for the large size but sparse distribution of 

 the fourth arm of the quadriradiate over the cloaca. Although 

 like the foregoing species in many respects, it differs from it 

 in general form and in the possession of a peristome. 



In the last three species the " articulated " portion of the 

 radial chamber is on the outside, the inside, and in the middle 

 respectively, while the other portions respectively are supplied 

 by the so-called " ^'^articulated " skeletal structure. 



Observation. 



Still following the structure of the " wall " for arrangement, 

 it becomes necessary to separate those species which present no 

 trace whatever of " radial chambers " from those which do, 

 although in a modified form, such as those last mentioned. 

 Hence they will be generically named " Heteropia^'' in 

 reference to the holes in the sarcodic structure of the wall, 

 which here is traversed by the shafts of more or less large 

 triradiates unaccompanied by smaller ones. 



Heteropia. 



Calcareous Sponges in which the wall is simply composed 

 of sarcode supported on large sagittiform triradiates, whose 

 heads are fixed in opposite sides of it respectively, and whose 

 long shafts, extending perpendicularly across it, more or less 

 overlap each other*. 



2 1 . Heteropia polyperistomia. 



Individualized, social. Globular, elongate, rather bent 

 upon itself, presenting six or more small, conical, glistening 

 peristomes scattered over the body, which is otherwise echi- 

 nated with thick, club-shaped, much curved, acerate spicules 

 directed forwards. Colour grey-brown. Surface consisting 

 of a rough, uneven, reticulate structure composed of the arms 



* A similar structure is represented by Hackel in his illustrations of 

 Sycilla (Atlas, Taf. 43. tigs. 6, 9, and 10) ; but to say that it is composed 

 of " Radial Tuben" appears to me to be a stretch of imajifination. 



