PLATE 64. 
Hyalonema (Hyalonema) placuna LeNDENFELD. 
Figs. 1-3, 5, 6, 9, 10, 12, 17-19 — form B. 
Figs. 4, 7, 8, 11, 13-16 —form A. 
1.— Centrotyle diactine spicule of form B; magnified 500; phot. Zeiss, apochr. 4, compens. oc. 6. 
2-7.— Microhexactines and pentactine microhexactine-derivates; magnified 500: 
2, 6, 7, phot. Zeiss, H. I. apochr. 2, compens. oc. 6; ’ 
3-5, phot. Zeiss, apochr. 8, compens. oc. 12; 
2, 3, 5, 6, of form B; 
4, 7, of form A. 
8.— Part of a paratangential section of the dermal membrane of form A, showing the lateral ray-crosses 
of the dermal pinules in situ; magnified 300; phot. Zeiss, apochr. 8, compens. oc. 12. 
9, 10.— Two lateral ray-crosses of dermal pinules; magnified 300: 
9, of form B; phot. Zeiss, apochr. 4, compens. oc. 6; 
10, of form B; phot. Zeiss, apochr. 8, compens. oc. 12. 
11.— View of the specimen of form A; natural size; phot. Zeiss, anastig. 480/412 mm. 
12.— View of the specimen of form B; natural size; phot. Zeiss, anastig. 480/412 mm. 
13.— Part of the oscular frill of form A; magnified 30; phot. Zeiss, planar 20 mm.: 
a, dermal pinules; b, longitudinal rhabds. 
14-19.— Side-views of dermal pinules; magnified 300: 
14-16, of form A; 
17-19, of form B; 
14-17, phot. Zeiss, apochr. 8, compens. oc. 12; 
18, 19, phot. Zeiss, apochr. 4, compens. oc. 6, 
