PLATE 39. 



Hyalonema (Hyalonema) obtusum gracilis Lendenfeld. 

 Figures 1-10. 



1. — An intermediate acanthophore with large spines, from the basal felt; magnified 300; phot. Zeiss, 



apochr. 4, compens. oc. 6. 

 2-4. — Slender-rayed acanthophore with long spines and parts of such, from the basal felt; magnified 



300; phot. Zeiss, apochr. 4, compens. oc. 6. 



5. — A very young he.xactine; magnified 300; phot. Zeiss, apochr. 4, compens. oc. 6. 



6. — Part of lean acanthophore from the basal felt; magnified 300; phot. Zeiss, apochr. 4, compens. oc. 6. 

 7-10. — Pachj'microhexactines from the basal part of the sponge; magnified 300; phot. Zeiss, apochr. 



4, compens. oc. 6: 



7, a small one with stout, nearly straight rays; 



8, a large one with more slender rays; 



9, 10, a large one with very stout rays; 



9, focussed higher; 10, focussed lower. 



Hyalonema (Hyalonema) obtusum robusta Lendenfeld. 

 Figures 11-41. 



11, 12. — Parts of intermediate acanthophores with large spines, from the basal felt; magnified 500; 

 phot. Zeiss, H. I. apochr. 2, compens. oc. 6: 



11, a central part of a triactine; 



12, the tip of a ray. 



13-16. — Parts of slender-rayed acanthophores with large spines, from the basal felt; magnified 500; 

 phot. Zeiss, H. L apochr. 2, compens. oc. 6: 

 13-15, tips of rays; 



16, the central part of a triactine. 



17-21. — Stout-rayed tetractine and tetractine-derivate acanthophores from the cement surrounding 

 the upper parts of the large stalk-spicule imbedded in the sponge-body; magnified 100; phot. 

 Zeiss, apochr. 16, compens. oc. 6: 



17, an angularly bent diactine; 

 18-20, tetractines; 



21, a triactine. 



22-24. — Parts of the felt, composed chiefly of the slender-rayed acanthophores with long spines, in the 

 basal part of the sponge: 



22, 23, magnified 300; phot. Zeiss, apochr. 4, compens. oc. 6; 

 24, magnified 100; phot. Zeiss, apochr. 16, compens. oc. 6. 



25, 26. — Uncinate amphioxes; magnified 100; phot. Zeiss, apochr. 16, compens. oc. 6. 

 27-29. — Parts of the uncinate amphiox represented in fig. 26; magnified 500; phot. Zeiss, H. L apochr. 

 2, compens. oc. 6: 



27, the end from which the spines diverge; 



28, the central part; 



29, the end towards which the .spines are inclined. 



30. — Part of an uncinate amphiox; magnified 2000; phot. Zeiss, q. monochr. 1.7, q. oc. 10. 



31, 32. — Two small, fairly regular hypodermal pentactines; magnified 50; phot. Zeiss, apochr. 16, 



compens. oc. 4: 



31, a side-view; 



32, an apical view. 



33. — View of the specimen; reduced 1: 0.85; phot. Zeiss, anastig. 480/412 mm. 



34-38. — Rhabd-acanthophores; magnified 100; phot. Zeiss, apochr. 16, compens. oc. 6. 



39. — An angularly bent diactine; magnified 100; phot. Zeiss, apochr. 16, compens. oc. 6. 



40, 41. — Larger hypodermal pentactines; magnified 50; phot. Zeiss, apochr. 16, compens. oc. 4: 



40, side-view of a fairly regular one; 



41, apical view of an irregular one with one of the lateral rays reduced. 



