PLATE 65. 



Hyalonema (Hyalonema) placuna Lendenfeld. 



Figs. 1, 3-13, 16-18, 23 — form B. 

 Figs. 2, 14, 15, 19-22 —form A. 



1. — A terminal anchor of a macramphidisc of form B, with a supernumerary tooth arising some distance 



below the others; magnified 500; phot. Zeiss, apochr. 8, compens. oc. 12. 



2. — Part of a mesamphidisc of form A; magnified 2000; u. v. phot. Zeiss, q. monochr. 1.7, q. oc. 10. 

 3-8. — Parts of a microhexactine of form B; magnified 2000; u. v. phot. Zeiss, q. monochr. 1.7, q. oc. 10: 



3, the centrum and a ray of the .spicule, focussed high (the tip of the ray in focus) ; 



4, part of the distal portion of the same ray, focussed lower (a region about 17 /x from the tip in focus) ; 



5, part of the middle-portion of the same ray, focussed still lower (a region about 32 yu from the tip in 

 focus) ; 



'6, part of the middle-portion of the same ray, focussed still lower (a region about 42 jx from the tip 

 in focus); 



7, part of the proximal portion of the same ray, focussed still lower (a region about 53 m from the tip 

 in focus); 



8, the basal part of the same ray and the centrum of the spicule, focussed lowest (the base of the 

 ray in focus). 



9-12. — Small internal pinnies of form B; magnified 300: 



9, phot. Zeiss, H. I. apochr. 2, compens. oc. 6; 

 10-12, phot. Zeiss, apochr. 4, compens. oc. 12. 



13-15. — Micramphidiscs; magnified 2000; u. v. phot. Zeiss, q. monochr. 1.7, q. oc. 10: 



13, a micramphidisc of form B; 



14, a micramphidisc of form A, focussed higher; 15, focussed lower. 

 16-21. — Internal pinules; magnified 300: 



16-18, of form B; 

 19-21, of form A; 



16, 20, 21, phot. Zeiss, apochr. 8, compens. oc. 12; 

 17-19, phot. Zeiss, apochr. 4, compens. oc. 6. 

 22, 23. — Radial sections through a superficial part of the sponge; magnified 30; phot. Zeiss, planar 

 20 mm.: 



22, of form A; 



23, of form B; 



a, dermal pinule-fur; b, choanosome. 



