80 OKHAMANDAL MARINE ZOOLOGY REPORT PART II 



suddenly to a moderately wide vent (Fig. 1). There is now no peristome, but it is 

 impossible to be certain that there were no hair-like oxea surrounding the vent in life. 

 The dermal surface is minutely reticulate, without conspicuously projecting oxea in 

 its present condition, but this is because the outer ends of the numerous large oxea 

 have all been broken off short. Size of specimen about 16 mm. high by 7 mm. in greatest 

 width. Texture soft and flabby. Colour in spirit white. 



The gastral cavity is wide, and the total thickness of the sponge wall only about 

 TO mm. The gastral surface is smooth and pierced by the numerous small apertures 

 of the exhalant canals. The dermal surface is formed by the fusion of the conical outer 

 ends of the radial chambers to form a reticulate pattern. The gastral cortex is moder- 

 ately thick and pierced by the short exhalant canals. The radial chambers taper towards 

 their distal extremities, while proximally they open, usually in groups, into the short 

 exhalant canals that pierce the gastral cortex. They are provided with well developed 

 diaphragms at the apopyles. They exhibit the " linked " arrangement described 

 by Jenkin [1908B] in his genus Tenthrenodes. The inhalant canals open on the dermal 

 surface by wide apertures between the distal conuli. 



The skeleton is typically syconoid in its arrangement, except that the usual tufts 

 of oxea which crown the distal ends of the chambers in typical species of the genus are 

 replaced by large oxea which cannot really be said to be arranged in tufts at all, but 

 extend sometimes through the entire thickness of the sponge-wall, between the 

 chambers, with their distal ends projecting from the surface more or less at 

 right angles. The articulate tubar skeleton consists of many joints, but there are 

 no specially differentiated subgastral sagittal radiates. The spicules are so much 

 broken and eroded that I have not found it practicable to get perfect specimens 

 suitable for figuring. The following descriptions, however, may be taken as 

 substantially correct. 



(1) Sagittal triradiates of the many- jointed articulate tubar skeleton ; with 

 very long and slender rays ; the oral angle wider than the paired angles ; the oral 

 rays curved around the chamber as usual and sometimes slightly and irregularly bent. 

 Dimensions of a specimen whose oral rays lie in about the middle of the chamber 

 wall : Basal ray about 0'2 by 0*005 mm. l ; oral rays about 0'12 by 0'005 mm. 



(2) Radiates of the gastral skeleton ; usually triradiate but sometimes with a 

 feebly developed apical ray. With wide oral angle and very long and slender 

 facial rays. These spicules are not definitely oriented but form a confused felt- 

 work in the gastral cortex, in which it is very difficult to follow the individual 

 rays for their entire length. I have measured the basal ray up to 0*4 mm. in 

 length, with an oral ray of about 0*2 mm., each having a diameter at the base 

 of about O'Ol mm., but they are usually rather more slender. 



1 The first measurement is the length and the second the greatest thickness in all cases except 

 where otherwise stated. 



