44 NATURAL HISTORY BULLETIN. 



Group I. — OphioUmna, gen. nov. Type, O.bairdii (Lym.) 



Spine-crest of the side arm-plates oblique and situated 

 distally. Spines nearly smooth. Disk granulose and spinulose. 

 Jaws more or less granulose. (See p. 40.) 



Group J. — Ophioprisi 'is, gen. nov. Type, O. hirsuta (Lym). 



A row of distal oral papillae alongside of the large, outer, 

 oral tentacle-pore. Arm-spines partly flattened, with serru- 

 late edges. (Seep. 40.) 



Group K. — Ophiotreta. subgen nov. Type, O. Uneolala 

 (Lym.) 



One or two flat, distal oral papillae by the side of the large 

 oral tentacle-pore. Two or three tooth-papillae. Spines 

 mostly terete, sometimes flattened and serrulate on the 

 edges. (See p. 40). 



Description of Species. 



Ophiacantha aspera Lyman. 



Ophiacantha aspera Lyman, Bull. Mus. Comp. Zool., V, 9, p. 228, pi. 

 I., figs. 10-12, 1878; op. cit., Vol. X, p. 263, 1883. Lyman, Report, 

 Voy. Challenger, Zool., Ophiuroidea, V, p. 199, 1882. 



The specimens collected show some minor variations among 

 themselves and differ considerably in details from Mr. Ly- 

 man's figures. 



The disk is densely covered with minute thorny spinules, 

 terminating in two to five or more short divergent points; 

 toward the margin they are longer, mostly with two or three 

 points. The mouth papillae are rather large and project 

 downward; there are sometimes 4, but oftener 3; they are 

 crowded and the innermost one is vertically compressed; the 

 two outer ones are often longer and larger, somewhat en- 

 larged and cuspidate at the end, and often rough with little 

 prominences like incipient thorns, showing a tendency to the 

 structure of the peculiar tentacle-scales; the two stand close 



