194 Scientific Proceedings, Royal Dublin Society. 



drical shaft with a whirl of spines at each end ; the spines may- 

 be sharp, but are more usually stunted and rounded off, or the 

 spines may be given off quite irregularly from all parts of the 

 shaft ; 0-016 by 0-012. Colour, deep puce black. 

 Habitat. — Port Jackson. 30-35 fms. 



Stryhnus unguicula, sp. n. — Sponge similar to S. niger. Dis- 

 tinguished by the forks, the arms of which are bifurcate, with the 

 primary rays extending, only slightly forward, and the secondary 

 rays diverted backward ; each pair of the latter, also, after diverg- 

 ing from each other in the usual way, are approximated so as to 

 run parallel to each other for the last half of their course ; shaft, 

 0*508 by 0-032 mm. ; primary rays, 0-0276, secondary rays, 

 0*04 mm. long. 



Habitat. — Port Elizabeth, S. Africa (not in Challenger Collec- 

 tion). 



Genus 8. Tribrachium, Weltner. — Sponge, a spherical body, 

 produced into an excurrent tube, but not into a special incurrent 

 tube. Spicules — forks, with only two arms in the excurrent tube, 

 with three arms in the cortex of the body ; acerates, anchors, rarely 

 stellates, and numerous sanidastra. 



Genus 9. Tethyopsis, Stewart. — Sponge, a special poral tube 

 at one pole of the spherical body and a special oscular tube at the 

 other ; canal system arranged on a radiate plan, primitively four 

 excurrent canals, alternating with four incurrent canals. Spicules — 

 reduced forks in the excurrent tube ; forks with three arms, or only 

 two or one in the cortex of the body, acerates, but no anchors ; 

 in the poral tube acerates, no forks or anchors; flesh- spicules are 

 stellates, sanidastra, and trichite sheaves. 



Genus 10. Psammastra, g. n. — Sponge, with a thick fibrous 

 cortex incorporating grains of sand ; oscules, two or more ; surface 

 raised into conuli ; spicules — a stellate with short rays and large 

 csntrum, and another form with smaller centrum and larger rays, 

 also, and most numerous spined bacilli ; forks of very peculiar 

 character, rays very short, appearing merely as spines of an 

 acerate spicule with a rounded distal end. 



