190 
THE VOYAGE OE H.M.S. CHALLENGER. 
Tethyopsis columnifera, Stewart. 
Tetliyopsis columnifer, C. Stewart, Monthly Micr. Journ., vol. x., N.S., p. 281, pi. xviii., 1870. 
Spo7ige more or less spherical, basal half torn away, produced into a special excurrent 
tube, the surface of which is raised into somewhat conical, compressed ridges, spirally 
arranged. Surface of the sponge incrusted with attached foreign bodies. 
Spicules.— 1. Megascleres. 1. Oxea, fusiform, 7'0 by 0'06 mm., rare. 
2. Somal orthotrisene, rhabdome 6 ’84 by O'll mm., cladi 0’4 mm. in length. 
3. Cloacal orihotrisene, with one cladus much elongated. 
II. Microscleres. 4. Ectosomal spheraster, minute, with a comparatively large 
centrum, actines reduced to rounded tubercles, 0 '00 8 mm. in diameter. 
5. Choanosomal chiaster, centrum small, actines numerous and slender, hair-like ; 
reminding one of a young form of sterraster, 0’02 mm. in diameter. 
6. Orthodragma, 0‘0276 mm. long; scattered through the choanosome. 
Colour. — White. 
Habitat. — Philippine Islands. 
Remarks. — The single specimen existing of this sponge is mutilated at the base, so that 
no traces of an incurrent tube, if it ever possessed one, remain. The sponge-body measures 
about 35 mm. in diameter, the cloacal tube 42 mm. in length by 7*5 mm. in diameter. 
The species differs in many respects from Disyringa dissimilis ; the two characters 
on which I rely for their generic distinction are primarily the absence of sanidasters in 
Tethyopsis columnifera, these being replaced by spherasters, and secondarily the absence 
of tangentially arranged oxeas in the cortex. 
Characters of minor importance are the general absence of disenes and monsenes in the 
sponge-body, and of modified dichotrisenes in the cloacal tube ; the absence of longi- 
tudinal tracts formed by the rhabdomes of the trisenes in the cloacal tube, excepting those 
which form the central axis, and as a consequence, the absence of a spicular framework 
for the support of the dermal membrane of the tube, this resting on the ends of the 
cladi of the trisenes and not on their sides. Orthodragmas, although present in Disyringa 
dissimilis, do not occur in the choanosome, while in Tethyopsis columnifera they do. 
Tethyopsis radiata (Marshall). 
Agilardiella radiata, Marshall, Ahhandl. d. k. Akad. d. Wiss. Berlin for 1883, 1884. 
Sponge. — Unknown, excurrent or cloacal tube cylindrical, rounded at the distal end, 
raised into eight long low ridges, separated by shallow’ groves, longitudinally and some- 
what spirally arranged, consisting of a small axial canal surrounded by eight larger 
peripheral canals. Ehabdomes of the orthotrisenes longitudinally disposed in the wall of 
the axial canals (or in the axis of the tube ?). 
