184 Scientific Proceedings, lloyal Dublin Society. 



large round, laterally placed, poriferous area, also lateral on the 

 opposite side to the oscule : both oscular and poriferous margins 

 fringed with long spicules. Rootlets few and slender. Flagel- 

 lated chambers, 0*063 mm. in diameter. Spicules — (I) fusiform 

 acerate, 10*07 by 0-026 mm., and 7*8 by 0-08 mm. ; (2) porrectate 

 forks, shaft, 5-88 by 0-087 mm. ; arms, 0-828 by 0-083 mm. ; 

 (3) bifurcated forks, shaft, 5-88 by 0-087 mm. ; primary rays, 

 0-238 by 0-0725 mm. ; secondary, 1193 by 0-06 mm. ; (4) somatic 

 anchor, shaft, 1-07 by 0-006 mm. ; rays, 0*048 mm. long; spread, 

 0-09 mm. ; (5) radical anchor, 1033 by 0-0175 mm. ; rays, 0-09 to 

 0*012 mm. ; spread, 0*123 mm. ; (6) calthrops small, with slender 

 rays, a single ray, 0*143 mm. long ; (7) smaller calthrops of usual 

 form ; (8) spini-spirulee, a stout spiral body, 0'0118 mm. long ; 

 spines, 0*016 mm. long. Greyish-white. 



Habitat.— Station 164 a, lat. 34° 19' S. ; long. 157° 31' E. 

 400 fms. 



Thenea icyvillii, sp. n. — Sponge, upper surface rounded, 

 cushion-like or flat, with a central, shallow, basin-like depres- 

 sion, in which the excurrent canals open by small, numerous, 

 oscula. Equatorial margin sharp, thin, without a spicular fringe, 

 projecting over the lower surface, which is produced into several 

 strong rootlets, ending below in a tangled spicular base. Poriferous 

 membrane continuous round the equatorial area. Spicules — 

 (1) acerate, 7*85 by 0*07 to 0*084 mm. ; (2) porrectate fork, 

 shaft, 6*8 by 0*072 mm. ; arms, 0*5 mm. long ; (3) bifurcate forks, 

 distinguished by the crooked form of these shafts, which measure 

 4*28 by 0-0968 mm. ; primary arms, 0*178 by 0*08 mm. ; secon- 

 dary, 0*54 by 0-064 mm. ; (4) somatic anchors, shaft, 0*876 by 

 0*008 mm.; rays, 0-95 mm. long; spread 0*1 mm.; (5) radical 

 anchors, 18*2 by 0*011 mm.; rays, 0*1 by 0*014 mm.; (6) cal- 

 throps, very regular, triradiate and quadriradiate, as well as other 

 forms; one ray of a quadriradiate measures from 0*08 to 0*09 by 

 0*0118 mm. ; (7) small calthrops; rays, from 4 to 10 in number, 

 about 0*02 mm. long; (8) spini-spirulae, a slender spiral shaft, 

 and numerous spines, total length, 0*02 to 0*025; length of a 

 single spine, 0*004 mm. Yellowish-white. 



Habitat— Station 209; lat. 10° 14' N.; long. 123° 54' W. 

 95 fms. 



