Victorian Fossils, Ft. K IS 



Summary. 



1. As a genus, Receptaculites ranges from the Silurian to 

 the Carboniferous in Australia,. The species R. axistralis is 

 probably coeval with the genus. 



2. The evidence here brought forward with regard to R. 

 australis shows — 



(a) The form of the sponge to be sub-discoidal or platter- 

 shaped, with a central funnel-shaped cavity. 



(b) Tlie horizontal spicule-rays are apparently derived from, 

 or fused to, the extremities of the vertical rays, at least in 

 the ' endorhin,' and partially so in the ' ectorhin.' 



(c) The structure of the horizontal spicular layer shows cer- 

 tain morphological resemblances to that of Sphaerospongia. 



(d) The original structure of the Receptaculites from the 

 Mount Wyatt beds, in common with those from Belgium, 

 Silesia and Canada (Hinde) has been pseudomorphosed by 

 peroxide of iron, nearly all of which replacement, in the case 

 of the Australian specimens, has since disappeared, the fossil 

 being represented by a negative cast in silica. 



(e) The evidence afforded by the pseudomorphosis of the 

 s^Donge by peroxide of iron, and its present siliceous epimorphic 

 condition, seems to lend strong support to the idea of an 

 oriainal siliceous structure. 



EXPLANATION OF PLATES IL-IV. 



Plate IL 



Fig. L — Receptaculites fergxisoni, sp. nov. Cast of the lower 

 or outer surface of the sponge. Silurian ; "Wombat 

 Creek, Victoria. [2317]. About natural size. 



,, 2. — Lower or outer siu-face of R. australis, Salter ; show- 

 ing the sub-rectangular form of the summit 

 plates. Middle Devonian ; Buchan, Gippsland. 

 [7509]. About natm-al size. 



,, 3. — A wax impression of oast of R. fergusoni, sp. nov. ; 

 showing the depressed rhombic summit plates and 



