NORTH PACIFIC OPHIURANS IN NATIONAL MUSEUM CLARK. 233 



tagonal, and wider than long; succeeding plates pentagonal, wider 

 than long, well separated from each other. Side arm plates short 

 but high, meeting broadly above and below; median area of each 

 plate elevated into a narrow, conspicuous ridge, as high as half the 

 diameter of the arm between the ridges. Each ridge carries eight or 

 nine straight, smooth, pointed spines, of which the middle ones are 

 longest and a little exceed two joints. Tentacle scales three on the 

 first two pairs of arm pores, and after that single; sharp and spine- 

 like, nearly as long as a joint. Color (dried from alcohol), yellow- 

 brown. 



Locality. Albatross station 4933, Eastern Sea, lat. 30 59' N.; long. 

 130 29' 50" E., 152 fathoms, rocky; bottom temperature 56, 1 

 specimen. 



Type. Cut. No. 25536, U.S.N.M., from station 4933. 



This single small specimen is in such poor condition that it is a pity 

 to designate it as the type of a new species, but nevertheless it shows 

 clearly such distinctive characters that no other course is open. The 

 mouth parts (including the oral shields), the very marked ridges on 

 which the arm spines are borne, and the very long, spine-like tentacle 

 scales are worthy of particular mention. 



OPHIACANTHA BATHYBIA, new species.a 



Disk 12 mm. in diameter; anus about 70 mm. long. Disk more 

 or less distinctly pentagonal, covered with very minute thorny 

 stumps. Radial shields concealed but their form and position are 

 indicated in dry specimens, through the skin ; they are long, narrow, 

 and well separated. Upper arm plates rounded triangular, tending 

 to rhombic, somewhat swollen, about as wide as long, all but first 

 two well separated. Interbrachial spaces below covered like the 

 disk. Genital slits fairly large. Oral shield very much wider than 

 long, with a somewhat rounded proximal angle and distal side only 

 slightly convex. Adoral plates large, three times as long as wide, 

 meeting broadly within; usually they partly inclose the oral shield, 

 sending a branch down between it and the side arm plate ; some- 

 times, however, they are wholly proximal to the oral shield which is 

 then in contact with the side arm plate. Oral papillae three or four 

 on a side, with sometimes an odd one at apex of jaw; outermost flat, 

 wide, and truncate; others narrower, thicker, and more pointed. 

 First under arm plate oblong, nearly twice as wide as long, barely in 

 contact with second which is broadly pentagonal or triangular, very 

 wide distally, with a somewhat curved margin; succeeding plates 

 similar but smaller, and relatively longer, well separated. Side arm 



BaOuc, signifying deep, and [Hof, signifying life, in reference to the great depth 

 at which it lives. 



