A. E, Verrill — North American Ophiiiroidea. 307 



It has three oral papiHos in a series, of which the middle one is 

 very large and flat, and the outer one small and spiniform ; the 

 apical one is large. The mouth-shield is so large that it touches 

 the first side-arm plate on each side, while the adoral shields are 

 yery small, not meeting within and not embracing the sides of the 

 mouth-shield, as they do in all the other divisions of Amphiura. 

 Two large tentacle-scales. Arm-spines very numerous, ten in the 

 type. Upper and under arm-plates in contact. Disk scales coarse 

 in the type. Radial shields separated. 



The type, (7. maxima (Lym.), is from the E. Indies in 28 fath. 



Amphiura Forbes (restricted sense). 



Amphiura Forbes, Trans. Linn. Soc, Vol. xix, pp. 149, 150, 1842 (type A. 



Chiajei). Ljungman, Ophiur. Viv., p. 318, 1867. 

 Amphiura (section B.) Lutken, Addit. Hist. Oph., ii, p. 114, 1859. 

 Atnphiura (pars) Lyman, Bull. Mns. Comp. Zool., i, pp. 335, 338 ; Voy. Cbal- 



lenger, v, pp. 122, 124, 1882. 

 Amphiura (restr.) Verrill, Ophiur. Bahama Exped., v, p. 24, 1897. 



Only one pair of true oral papillfe to each mouth-slit ; they are 

 placed on each side of the apex of the jaw. A single, usually spini- 

 form, papilla, sometimes with a smaller one by its outer side, is 

 situated on each side of the distal end of the mouth-slit, usually 

 attached to the edge of the adoral shield. This is really the outer 

 oral tentacle-scale. 



Owing to the small number of oral papillae and their peculiar 

 arrangement, the mouth slits cannot be closed, but appear always 

 gaping, more or less. 



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

 Higher ujj in the mouth-slit there is a small spiniform 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 

 oral papilla. Tentacle-scales usually one or two, sometimes lack- 

 ing (section Ophioj^elte). 



Ai-m-spines short, usually four to seven or more, rarely three. 

 Radial shields naked, small, generally* divergent, with the distal 

 ends either in contact or somewhat separated by small scales. The 

 disk is usually covered with small naked scales. 



In one group the under side is without scales {Hemilepis). 



In a group referred by Lyman to Ophiocnida, the disk is covered 

 with small spinules, but as the mouth-parts and other organs agree 

 with typical Amphiura, it might better be regarded as a distinct 

 genus, or else as a subgenus of Amphiura. To this I have given the 

 name Amphiocnida. (See p. 316.) 



