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. 



I. — 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. 



II. — 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. 



