} 
PLATE 106. 
Euretid. Station 4641. 
Figures 1-3. 
1.— Part of the gastral face of the skeleton of the tube-wall; magnified 30; phot. Zeiss, planar 20 mm. 
2. Part of the dermal face of the skeleton of the tube-wall; magnified 30; phot. Zeiss, planar 20 mm. 
3.— View of the skeleton; natural size; phot. Zeiss, anastig. 480/412 mm. 
Hyalonema (Prionema) crassum LENDENFELD. 
Figures 4-37. 
- 4-12.— Microhexactines; magnified 200; phot. Zeiss, apochr. 8, compens. oc. 6: 
4-6, the same microhexactine; 
4, focussed high; 5, focussed on the centre of the spicule; 6, focussed low; 
7-10, different microhexactines; 
11, 12, a group of microhexactines in a spicule-preparation; 
11, focussed higher, 12, focussed lower. 
13-20.— Micramphidises; magnified 500; phot. Zeiss, H. I. apochr. 2, compens. oc. 4. 
21-25.— Micramphidises; magnified 2000; u. v. phot. Zeiss, q. monochr. 1.7, q. oc. 10: 
21-23, the same micramphidise; 
21, focussed high: 22, focussed 0.7 » lower; 23, focussed 1.4 » lower; 
24, 25, two different micramphidises. 
26-30.— Pinules; magnified 300; phot. Zeiss, apochr. 8, compens. oc. 12. 
31.— A microhexactine (of which only two opposite rays are in focus); magnified 500; phot. Zeiss, 
H. I. apochr. 2, compens. oe. 4. 
32-37.— Rays of microhexactines; magnified 2000; u. v. phot. Zeiss, q. monochr. 1.7, q. oc. 10: 
32, the basal quarter of a ray, focussed low; 
33, the basal half of the same ray, focussed higher; 34, focussed still higher; 
35, the distal third of the same ray focussed highest; 
36, the tip of another ray; 
37, another ray. 
