206 PHYLUM ECHINODERMATA. 



Ophiocten Ltk. ; Gymnophiura Mrtsn. British species : Ophiura ciliaris, 

 E. X. Atl., 7-100 fms. ; 0. albida, ditto, to 250 fms., O. affinis, ditto, 

 10-192 fms. 



2. Spines at right angles to the arm axis. 



Fam. 3. Amphiuridae. With 1 to 5 oral papillae, the innermost 

 often infradental. Arms inserted on the ventral side of the disc. Dental 

 papillae absent. Ophiambyx Lym. ; Ophiopholis M. and T. ; Ophiostigma 

 Ltk. ; Ophiochiton, Hemipholis, Amphilepis, Ophiocnida, Ophiophragmus, 

 Ophiopla.r, Ophiochytra, Ophiomyces, all Lym. ; Ophiopits~Ljg. ; Ophiactis 

 (Fig. 142) and Opliionereis Ltk.; Amphiura and Ophiopsila Forbes; 

 Paramphiura Khlr. ; British species: Amphiura chiajii, to 120 fms ^ 

 A. filijormis, to 120 fms. ; A. elegans, to 120 fms. Ophiactis abyssicola, 

 64 to 767 fms. ; 0. balli, to 203 fms. Ophiopholis aculeata to 300 fms. 

 Ophiacantha bidentata, 20-2,335 fms. 



Fam. 4. Ophiohelidae. Disc with scales and sharp or blunt spines,, 

 with teeth and oral papillae, without dental papillae. Ophiomitra, 

 Ophiothamnus, Ophiocamax, Ophiotholia, all Lym. 



Fam. 5. Ophiacanthidae. Disc covered by soft skin, which more 

 or less hides the subjacent scales ; dental papillae absent or few. Ophia- 

 cantha il. and T. ; O. vivipara Ljn., 6 or 7 arms ; 0. anomala G. O. Sars, 

 6 arms. Ophiolebes, Ophiotoma, Ophiogeron, Ophiosciasma, Lym. : Ophio- 

 blenna, Ophionema, Ophionephthys Ltk. ; O phiocentrus Ljg. ; Ophioscolex 

 M. and T. ; Ophiotrema Khlr. Brit. sp. : Ophioscolex glacialis, 100-300 

 fms., 0. purpurei, 64 to 76 fms. 



Fam. 6. Ophioeomidae. With oral and dental papillae. Ophio- 

 cymbium Lym. ; Ophiocoma L.Ag. ; Ophiarachna and Ophiomastix 

 M. and T. ; Ophiopteris E. Sm. ; Ophiarthrum Ptrs. British species r 

 Ophiocoma nirjra. to 87 fms. 



Fam. 7. Ophiotrichidae. With 8-10 dental papillae, without oral 

 papillae. Ophiopteron and Opltiotrichoides Ludw. ; Ophiothrix and 

 Ophiocnvmis M. and T. ; Ophiocampsis Dune. ; Ophiomaza and Ophio- 

 psammium Lym. ; Ophiothela Verr. ; Ophiogymna Ljg. ; Luetkenia, 

 Gymnolophus, Ophioaethiops, Ophiosphaera Brock. Brit. sp. : Ophiothrix 

 frag His, to 52 fms. 



Order 3. STEEPTOPHIUEAE. Astrophytoii-like Ophiurae. 



The ambulacral ossicles articvilate with one another by means of a 

 more or less simple ball-and-socket joint, and the arms can be moved 

 in a vertical direction and be coiled towards the mouth. Upper, under, 

 and side plates are more or less regularly developed : the side plates 

 bearing spines. 



Fam. 1. Ophiomyxidae. With 3-7 oral papillae, without teeth. 

 Arms covered with soft skin. Neoplax Bell ; Ophioteresis Bell, no under 

 arm-plates ; Ophiobyrsa, Ophiochondrus, Sigsbeia and Ophiobrachion 

 Lym. ; Ophiomyxa M. and T. ; Hemieuryale Martens ; Astrophis A. M. 

 Edw. ; Ophiohclus. 



Several extinct families come here, viz., Ophiurinidae, Lapworthidae, 

 Eoluididae, Onychasteridae, Eucladiidae. The Eucladiidae from th& 

 middle Silurian of England have short arms, and a ventral madreporite. 

 Each arm has 2 or 3 arm -like branches ; these are tube-feet with a flexible^ 

 armour of minute spiny scales. Eudadia H. Woodward, Euthemon. 

 Sollas. 



