MoNOGIÎArH OF JAPANESE OrHIUROlDEA. 169 



+ 11 +III, two or three ou either side, discontinuoiis, the iufradeutal 



and distal ones being separated from each other by a wide interval ; 



oral slits gaping ; an additional papilla present just outside and 



above the infradental one ; radial shields divergent or separated 



from each other. 

 g — Disk entirely free of spines. 

 h — No supplementary plates between the oral plates and the adorai 



shields. 

 i — Oral shields not very stout, not in contact with the iîrst lateral 



arm plates. 

 ./ — Disk entirely or partially covered ^ith fine scales ; radial shields 



not very narrow and bar-like Amphinra. 



jj — Disk entirely covered by a smooth naked skin ; radial shields 



exceedingly narrow and bar-like OpJiionema. 



it — Oral shields very stout, in contact with the first lateral arm plates ; 



two distal oral papiUae, of which the outer one is small and 



spiniform, while the inner one is very large and flat ; ten arm 



spines Ctenamphiurœ 



Jih — Two supplementary plates present between the oral plates and the 



adorai sliields of each interradius ParampJdura. 



(J g — Disk beset with numerous spines OpJdocentrus. 



Key to Japanese species of Aniphioplns. 



A — Two tentacle scales to each pore. 

 a — Three arm spines. 



^ — Tentacle scales unusually large, nearty closing the large pores ; 

 ventral arm plates much wider than long ; disk unknown .... 



megopomus. 



l>b — Tentacle scales small, not closing the large pores ; ventral arm 

 plates longer than wide ; radial shields slender, partly joined in 



pairs rhadinohracldus. 



aa — Four or more arm spines. 



