OPHIUROIDEA OF THE BAHAMA EXPEDITION. 25 



III. Amphiodia, gen. nov. Type A. pulchclla (Lym.) 



Three (rarely four) small subequal mouth papilla?, none of 

 them operculiform; they form a regular series, attached most- 

 ly to the side jaw-plate. Three (rarely four) arm-spines. 

 Radial shields often more or less joined. 



IV. Amphiophis, gen. nov. Type A. tumida (Lym.) 



Four or five small mouth-papilla?, none operculiform, ar- 

 ranged in a continuous series, of which the outermost, at 

 least, arises from the adoral shield and is really an oral ten- 

 tacle-scale. Arm-spines three, (rarely four). Radial shields 

 generally quite separated Disk scales naked. 



Amphiura Forbes (restricted sense). 



Amphiura Forbes, Trans, Einn. Soc, Vol. XIX, pp. 149, 150, 1842, 

 (type A. chiajei) Ejung-man, Ophiur. Viv., p. 318, 1867. 



Amphiura (section B. ) Eutken, Addit. Hist. Oph., II, p. 114, 1859. 



Amphiura {pars) Lyman, Bull. Mus. Comp. Zool., I, pp. 335, 338; 

 Voy. Challenger, V, pp. 122, 124, 1882. 



Owing to the small number of mouth-papillae and their pe- 

 culiar arrangement, the mouth slits cannot be closed, but ap- 

 pear always gaping, more or less. 



Only one true mouth papilla, which is placed on each side 

 of the apex of the jaw. A single, usually spiniform, papilla, 

 sometimes with a smaller one by its outer side, is situated at 

 the distal end of the mouth-slit, usually attached to the edge 

 of the adoral shield. This is really the outer oral tentacle- 

 scale. 



The edge of the jaw-plate, along its middle portion, is 

 naked. Higher up in the mouth-slit, there is a small spini- 

 form papilla, usually visible from below; this is the tentacle- 

 scale of the first oral tentacle. It is often shown in published 

 figures as if it were a true mouth-papilla. Tentacle-scales 

 usually one or two, sometimes lacking (section Ophiopelte). 



