206 PHYLUM ECHINODERMATA. 



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

 E. N. Atl., 7-100 fms. ; O. albida, ditto, to 250 fms., O. afflnis, 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, 

 Ophioplax, Ophiochytra, Ophiomyces, all Lym. ; Ophiopus Ljg. ; Ophiactis 

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

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

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

 64 to 767 fms. ; O. 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 M. 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. ; Ophiocentrus Ljg. ; Ophioscolex 

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

 fms., O. purpurea, 64 to 76 fms. 



Fam. 6. Ophiocomidae. 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 nigra, to 87 fms. 



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

 papillae. Ophiopteron and Ophiotrichoides Ludw. ; Ophiothrix and 

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

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

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

 fragilis, to 52 fms. 



Order 3. STREPTOPHIURAE. Astrophyton-like Ophiurae. 



The ambulacral ossicles articulate 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. ; Ophiohelus. 



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

 Eoluididae, Onychasteridae, Eucladiidae. The Eucladiidae from the 

 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. Eucladia H. Woodward, Euihemon 

 Sollas. 



