OPHIURANS OF THE PHILIPPINE AND ADJACENT WATERS. 55 



The under and side arm plates on the lower surface show fine con- 

 centric striations. On the under arm plates these striations at first 

 have their concavity directed toward the arm tip, while in the last 

 third of the plates these striations have the concavity directed toward 

 the mouth. On the upper arm plates these striations are scarcety 

 indicated, or may even be entirely lacking. 



The singles tentacle scale is very large, flattened, lanceolate, and 

 pointed, and on the free border in the distal half bears some fine 

 spinules, which cause it almost to justify the appelation spiniferous. 



Affinities and distinctive features. Ophiacantha legata approaches 

 most closely O. aspera Lyman. It differs from it in the character 

 of the club spines of the dorsal surface of the disk, which are much 

 elongated, in the pointed tentacle scales provided merely with a few 

 rather fine spinules instead of possessing those lobes which are so 

 marked in O. aspera, in the shorter mouth shields, in the longer 

 mouth papillae, and in the more elongated under arm plates. 



It is also close to O. longidens Lyman, which lives at a lesser depth ; 

 it is distinguished from that species by its more broadened and 

 shorter mouth shields, and by its more numerous and strongly echin- 

 ulated arm spines; furthermore, the dorsalmost spine always show 

 very strong and well spaced teeth, and the two lateral series of spines 

 are perfectly continuous on the first arm segments; the upper arm 

 plates are shorter, the tentacle scales bears fine spinules, and the club- 

 spines of the dorsal surface of the disk are stronger and terminated 

 by shorter and more pointed spinules in 0. legata than in O. longi- 

 dens. 



OPHIACANTHA LONGIDENS Lyman. 



Plate 17, figs. 6, 7. 



Locality. Albatross station 5153; Sulu (Jolo) Archipelago, Tawi 

 Tawi Group ; Tocanhi Point bearing S. 27 E., 3.89 kilometers, (2.1 

 miles) distant (lat. 5 18' 10" N., long. 120 02' 55") ; 90 meters (49 

 fathoms) ; February 19, 1908; co. S., Sh. 



One specimen (Cat. No. 41236, U.S.N.M.). 



Notes. It is not without much hesitation that I refer this speci- 

 men to O. longidens Lyman. As yet that species is known only from 

 a single individual captured in the Philippines by the Challenger at 

 a depth of between 174 and 183 miles (95 and 100 fathoms). As the 

 description given by Lyman is very brief, I requested my colleague, 

 Prof. F. J. Bell, to compare with Lyman's type the photographs 

 which I sent him of my specimen, and his opinion was that they both 

 represented the same species, an opinion which he gave, however, 

 with reservations, for, he wrote me, the very small type is in rather 

 bad condition, two arms only being preserved and these broken off. 



