Geschichte des Systems. 909 
2) Trichasteridae: Cladophiurae with arms branching a few times 
near their free ends. 
Genera, recent: — Trichaster L. Ag., Astroclon Lym.; Astrocnida 
Lym., Fossil: — Astroenida Lym. 
3) Gorgonocephalidae: Cladophiurae with arms branching much 
and from their base. Buryale Lam., Gorgonocephalus Lym., Astro- 
phyton Ag., Ophiocrene Bell. 
Ord. IV. Zygophiurae J. Bell, 1892 
mit den Familien: 
l) Ophiodermatidae: Zygophiurae with oral papillae numerous, 
and none infra-dental. Arm incisures on the disc. Dental papillae 
absent. 
Genera — Ophioderma Müll. und Trosch., Ophiopeza Peters, 
Ophiarachna Müll. u. Trosch., Ophiocoeta Lütk., Ophioconis 
Lütk., Ophioplax Lym., Ophiogona Stud. (2), Ophiopyrgus Lym., 
Ophropyren Lym. 
2) Ophiolepididae: Zygophiurae with oral papillae from three to 
six, of which the last may be infradental. Arm ineisures on the 
disc. Dental papillae absent. 
Genera — Ophiolepis Müll. u. Trosch., Ophiocten Lütk., Ophiura 
L. Ag., Ophioglypha Lym., Ophioceramis Lym. (2), Ophiochiton 
Lym., Ophiopaepale Lym., Ophiozona Lym., Ophioplinthus Dan., 
Amphiglypha Pohl., Geocoma d’Orb. 
3) Amphiuridae: Zygophiurae with oral papillae from one to five, 
of which the last is generally infradental. Arms inserted on 
ventral side of disc. Dental papillae absent. 
Genera — Amphiura Forbes, Ophioenida Lym., Ophiomusium 
Lym., Ophiopeltis Daniels. u. Kor., Ophiocentrus Ljung., Amphi- 
lepis Ljung., Ophiolepis Lym., Ophiomastus Lym., Ophio- 
phyllum Lym., Ophiotrochus Lym., Hemipholis Lym., Ophiactis 
Lütk., Ophiopus Ljung., Ophiopholis Lütk., Ophiacantha Müll. 
u. Trosch., Ophiotrema Koehl.. Peetinura Heller (non Forbes), 
Ophioplocus Lym., Ophionereis Lütk., Amphipholis Ljung., 
Ophiophragmus Lym., Ophiostigma Lütk., Ophioblenna Lütk., 
Ophiocymbium Lym., Ophiochytra Lym., Ophiolebes Lym., 
Ophiomitra Lym., Ophiocamax Lym., Ophiothamnus Lym., 
Acroura Ag., Aspidura Ag., Hemiglypha Pohl., Polypholis Dunc. 
4) Ophiocomidae: Zygophiurae with both oral and dental papillae. 
Genera — Ophiocoma L. Ag., Ophiomastixe Müll. u. Trosch., 
Ophiarthrum Pet., Ophiopsila Forbes, Ophiopteris E. A. Smith. 
