0PHITJR0IDEA. 



25 



Order 1. ZYGOPHIUBJE. 



Ophiurae (pars), Forbes, Brit. Star/. (1840) p. 21 ; M. Tr. Syst. Ast. 



1 1 n a a \ . _ no 



OphiuridsB (pars), Lyman, III. Cat. M.C.Z. (1865) p. 5 ; Norman, 



Ann. $ Mag. xv. (1865) p. 106. 

 Ophiastra (pars). Haeckel, den. Morphol. ii. (1866) p. lxvi. 

 Zygopnhme, Bell, P. Z. 8. 1892, p. 180. 



Ophiuroids with the faces of the arm-ossicles more or less dis- 

 tinctly provided with articulating knobs and pits, which prevent 

 the ossicles from being coiled, or rolled towards the mouth. In 

 nearly all the central ossicles are surrounded by an upper or lower 

 and two lateral plates ; the last bear few or several spines of vary- 

 ing length and strength. The arms are never branched. The clefts 

 at the base of the arms always open into bursae. Mouth, tooth- 

 papillae, and true teeth may all be found, and are never all wanting. 

 Mouth-shields and side mouth-shields present. A single madre- 

 porite. No pedicellarise. The tentacular pores very often covered 

 by one or two scales. 



I. Without tooth-papilla?. 

 A. Arm-incisions on the disk. 



Family 1. OPHIOLEPIDIDtE. 



Ophiolepididae, Ljungman, CEfv. Vet. Akad. Fbrhlg. 1866 (1867), 

 no. 9, p. 306. 



Oral papilla? three to six ; radial shields naked ; spines smooth ; 

 mouth-shields moderate or large, often produced into the inter- 

 brachial spaces. 



Two genera : Ophiura and OpJiiocten. 



Incertae sedis : Ophiochiton. 



B. Arms inserted on ventral surface of disk. 



Family 2. AMPHIURHLE. 



Amphiuridae, id. t. c. p. 309. 



Oral papilla? one to five ; radial shields naked : spines smooth, or 

 more or less rough : mouth-shields small, not produced into inter- 

 brachial spaces. 



Seven genera: Ophiornusium, OpMocnida, Awphiura, Opftiactis, 

 Ophiopus, Ophiopholis, and Ophiacantha. 



