PLATE 63. 



Hyalonema (Prionema) fimbriatum Lendenfeld. 

 Figui-es 1-28. 



1-5. — Hexactine megascleres; magnified 50; phot. Zeiss, achr. aa, compens. oc. 6. 

 6-9. — Hypodermal pentactines; magnified 50; pliot. Zeiss, achr. aa, compens. oc. 6: 



6, apical view; 



7-9, side-views. 



10-14. — Rhabd megascleres; magnified 50; phot. Zeiss, achr. aa, compens. oc. 6: 

 10, 11, amphiox rhabds; 



12-14, rhabds rounded and thickened at one end. 

 15-28. — Acanthophores ; magnified 100; phot. Zeiss, apochr. 16, compens. oc. 6: 

 15, a small tetractine; 



16-18, large tetractines with fairly equal rays; 

 19, a large tetractine with unequal rays; 



20-24, straight or only slightly curved, more or less centrotyle diactines; 

 25, 26, slender, strongly curved, terminally thickened rhabds; 

 27, 28, stout, curved, terminally thickened rhabds. 



Hyalonema (Hyalonema) placuna Lendenfeld. 



Figs. 29-34, 36-41, 51 — form B. 

 Figs. 35, 42-50 —form A. 



29-34. — Mesamphidiscs of form B; magnified 500; phot. Zeiss, apochr. 4, compens. oc. 12. 

 35. — A mesamphidisc of form A; magnified 500; phot. Zeiss, H. I. apochr. 2, compens. oc. 6. 

 36-41. — Micramphidiscs of form B; magnified 500: 



36, 39, phot. Zeiss, apochr. 4, compens. oc. 12; 



37, 38, 40, 41, phot. Zeiss, H. I. apochr. 2, compens. oc. 6. 



42-45. — Micramphidiscs of form A; magnified 500; phot. Zeiss, H. I. apochr. 2, compens. oc. 6. 

 46, 47. — Centrotyle amphioxes of form A; magnified 100; phot. Zeiss, apochr. 16, compens. oc. 6. 

 48-50. — Hypodermal pentactines of form A; magnified 100; phot. Zeiss, apochr. 16, compens. oc. 6: 



48, an apical view; 



49, 50, side-views. 



51. — Part of a tetractine mesamphidisc-derivate (tetradisc) of form B; magnified 500; phot. Zeiss, 

 apochr. 8, compens. oc. 12. 



