OPHIURANS OF THE PHILIPPINE AND ADJACENT WATERS. 45 



internal is very much narrower although almost as long as the first; 

 this internal scale may be lacking on certain pores, or it may be so 

 small as to be completely hidden by the external scale. 

 The color of the specimen in alcohol is grayish white. 



OPHIACANTHA BENIGNA, new species. 



Plate 16, figs. 5, 6. 



Locality. — Albatross station 5592 ; Sibuko Bay, Borneo, and vicin- 

 ity; Silungan Island (M.) bearing N. 1° W., 11.86 kilometers 

 (6.4 miles) distant (lat. 4° 12' 44" ST., long. 118° 27' 44" E.) ; 558 

 meters (305 fathoms) ; September 29, 1909 ; gn. M. 



One specimen (Cat. No. 41235, U.S.N.M.). 



Descriptio?i. — The diameter of the disk is 5 mm. ; tl\e arms are 

 about 20 mm. in length, and are more or less rolled up. 



The disk is subpentagonal. The dorsal surface is covered with 

 small, short, closely crowded club-spines with their bases greatly 

 broadened, each one inserted upon a small rounded plate, which is 

 not very distinct and which can only be made out on certain portions 

 of the disk. These club spines taper rapidly and terminate in a crown 

 of four or five very short and divergent spinules. The radial shields 

 are distinct; they are small, triangular, a little longer than broad, 

 and not in contact though rather close to each other. 



That part of the ventral surface which lies beyond the mouth 

 shield in the interradial spaces is insignificant; it is covered with 

 little club-spines similar to those on the dorsal surface, but smaller. 

 The genital slits are rather broad. 



The mouth shields, which are of medium size, are a little broader 

 than long, triangular, with a rather open proximal angle bounded by 

 two slightly concave sides, and the distal side strongly convex with 

 rather sharp lateral angles. The adoral plates are extremely broad, 

 and their longer borders are almost parallel ; they are half again as 

 broad as long, scarcely narrower outwardly than inwardly. The oral 

 plates are triangular and rather high. The lateral papillae are three 

 in number (I find in one instance four of them) rather small, short, 

 and conical, but the distal papilla is a little more broadened than the 

 others; the unpaired terminal papilla is thick and strong. The sur- 

 face of these papillae is very rugose. 



The upper arm plates are small and triangular with a proximo 1 

 rather open angle and a rounded distal border. The first two or 

 three are a little broader than long, the following becoming almost as 

 long as broad. They are separated from the base of the arm outward 

 by a rather broad interval. 



The first under- arm plate is quadrangular, a little longer than 

 broad, with a broad and slightly excavated proximal border, and a 



