90 ProceediiKj.s of the Royal Society of Victoria. 



22. GrayitiopHis cyliiuirica, n. sp. 



Sponge forming long, cylindrical tubes, which may branch, 

 with single, terminal, slightly constricted, almost naked 

 oscula. Sui'face not hispid but slightly roughened by the 

 large triradiate spicules of the cortex. Tlie largest tube in 

 the collection is unbranched and slightly crooked, 57 mm. 

 long and with a nearly uniform diameter of 5 mm. 



'i'he wall of the tube is about 1 mm. in thickness, and is 

 divided into two sharply defined concentric laj^ers of about 

 equal thickness. The outer of these layers forms a firm 

 cortex with a very strongly developed skeleton. , The inner 

 la3'er is soft and spongy, consisting almost entirely of the 

 radial chambers, which have but a feebly developed tubar 

 skeleton. 



The iidialant pores, scattered in groups over the dermal 

 surface, lead into veiy sharply defined, wide inhalant canals, 

 which penetrate the cortex, uniting into larger trunks which 

 conduct the water to the ordinary' " intercanals" between 

 the radial chambers. 



The radial chambers ai'e ari-anged side by side with great 

 regulaiity. Each is a straight, wide, unbranched (or very 

 sliglitly blanched) tube, extending completely through the 

 chain] )er layer. In cross section they vary from nearly 

 square to neai-l_y circular. Each o])ens directly and separately 

 into the gastral cavity, the gastral cortex being so tliin tliat 

 no special exhalant canals are required. Kacli is provided 

 at its i)roximal end with a membranous diaphragm, which, 

 in the s]nrit specimen, almost closes the Oj)eniiig. 



The arraiigement of the skeleton is a slight modilication 

 of t!)e Gravtia type, but the spiculation is xevy peculiar, as 

 follows: — (1) Gastral quadriradiates ; sliiilitly sagittal, with 

 small facial and enormous apical rays ; the oral angle is rather 

 wider than die lateral angles, but tliere is not much difference 

 in the length of the facial ra_ys, which are nearly straight 

 (the orals may be sliuhtl}' curved), fairly stout, conical and 

 graduallj' sharp-pointed, about 0-056 by O'OOT mm. The 

 apical ray is slightly curved, very .stout, sword-shaped in 

 optical section, thickest hi about the middle, gradually 

 sharp-pointed, about 014 by 001 4 mm. These apical 

 rays thickly echinate the gastral surface. (2) Subgastral 

 quadriradiates; strongly sagittal; the oral rays very widely 

 extended and parallel to the gastral surface ; the basal ray 

 extending centrifugally towards the dermal surface through 



