PLATE 34. 
Hyalonema (Hyalonema) obtusum gracilis LENDENFELD. 
Figures 1-19. 
1.— Section vertical to the surface, through a superficial part of the sponge; magnified 30; phot. Zeiss, 
planar 20 mm.: 
a, dermal membrane; b, subdermal cavities; c, a hypodermal pentactine with reduced ‘and 
terminally rounded apical ray. 
2.— Radial section through the choanosome; magenta; magnified 100; phot. Zeiss, apochr. 16, ‘compens. 
oc. 6. 
3.— Axial section through the oral cone and the adjacent parts of the upper end of the sponge; magenta; _ 
magnified 5; phot. Zeiss, planar 50 mm.: 
a, outer surface (dermal membrane); b, narrow fissure-like gastral cavity between the oral cone 
and the oral frill; ce, summit of the oral cone. 
4.— Axial section through the lower part of the sponge; magenta; magnified 5; phot. Zeiss, planar 50 mm. 
5-18.— Choanosomal hexactines of the supporting skeleton; magnified 50; phot. Zeiss, achr. aa, oc. 2: 
5-7, 10, 12, situated with one axis (two rays) parallel to the optical axis, and two axes (four rays) in 
a plane vertical to the optical axis; 
8, 9, 11, 13-18, situated with the tips of three of the rays in a plane vertical to the optical axis; 
5-7, 11, 15, 16, 18, medium-sized hexactines; . 
8, 10, 13, 17, large hexactines; 
9, 12, 14, small hexactines. 
19.— Radial section through the superficial part of the sponge; magnified 100; phot. Zeiss, apochr. 16, 
compens. oc. 6: 
a, dermal membrane; b, group of small.macramphidises: c, subdermal cavity; d, hexactines 
of the supporting skeleton. 
