OPHIUROIDEA OF THE BAHAMA EXPEDITION. 27 



six on the basal half of the arms; they are of moderate length, 

 rather slender, tapered; the lower one, especially on the mid- 

 dle part of the arm, is longer than the others, sometimes 

 twice as long, and somewhat bent downward; the upper one 

 on this part of the arm is often stouter and a little longer 

 than the intermediate ones. Upper arm-plates rather broad- 

 er than long, in contact, somewhat trapezoidal, with the 

 distal end convex and the angles rounded, the lateral edges 

 convergent, the inner end narrower and truncated; the ex- 

 treme outer edge is sharp, thin, and microscopically serru- 

 late. Under arm-plates oblong, longer than broad, with 

 rounded corners and concave lateral edges, opposite the ten- 

 tacle-pores, outer end convex, inner end subtruncate. Ten- 

 tacle-scale single, rather large for the genus, thick, rounded 

 or broad-ovate, obtuse. Oral shield small, transversely broad 

 elliptical, evenly convex distally, inner side with a slight ob- 

 tuse angle. 



Adoral shields small, triangular, inner end acute; generally 

 the inner ends are not in contact. Inner mouth-papilla short, 

 thick, conical; outer one, (oral'tentacle-scale) thicker, short- 

 conical, obtuse; sometimes there is another rudimentary one 

 alongside of the latter, and like it arising from the adoral 

 shield. The inner oral tentacle has a small, thick, acute pa- 

 pilla in the middle of the mouth-slit, above the level of the 

 others. 



Diameter of the disk of the largest specimen, 7 mm; length 

 of arms, about 25 mm. 



Stations 54 and 58, off Florida, 130 fathoms. Taken by 

 the Blake Exped. in 10 to 262 fathoms. 



The specimens from the Blake Exped., station 319, in 262 

 fathoms, differ from the above in some minor points. The 

 disk-scaling is a little less fine; the radial shields a little broad- 

 er, and the arm-spines a little smaller, but they vary among 

 themselves in these characters. 



This species is allied to O. often', but has much shorter, 

 more delicate and more tapered arms, and the lower spine is 



