NOKTII PACIFIC OPHIURANS IN NATIONAL MUSEUM CLARK. 59 



even more numerous than on disk. Oral shield large, about as wide 

 as long, somewhat pentagonal, with a broad, proximal angle and a 

 straight distal margin. Adoral plates variable, sometimes appar- 

 ently confined to inner end of oral shield, but usually reaching the 

 first side arm plates; oral plates large, usually much larger than 

 adoral. Oral papillse five on each side, well spaced, outermost wid- 

 est and truncate, inner ones narrow and sharp; an infradental papilla 

 is often present. Teeth about six, moderately wide, pointed. Gen- 

 ital slits long, proximal end nearer center of mouth than is distal 

 end of a mouth slit. Genital scales large, upper, outer end very 

 broad; each scale has a marginal fringe of very minute papillse which 

 become rapidly elongated distally into very slender spines, forming a 

 well-marked arm comb, when viewed from above. Beneath this comb 

 on the basal arm plates is a smaller secondary comb, wdiich extends 

 inward between ends of radial shields and is often very conspicuous. 

 Under arm plates much wider than long; first two decidedly largest 

 and more or less (dearly in contact; succeeding plates wideh' sepa- 

 rated, becoming rapidly smaller, oblong-hexagonal, pentagonal, or 

 tetragonal. Side arm plates rather large, but low and meeting only 

 on lower side of arm; each plate carries three arm spines, of which 

 uppermost is longest, but does not equal joint; other two much 

 smaller, close together near lower edge of, plate. Tentacle pores at 

 base of arm large but quickly becoming much smaller; oral and basal 

 arm pores guarded by about three scales on each side; further out 

 on arm there are three and then two scales on proximal side of 

 pore, and finally onh" a single scale is present. On oral pores, ten- 

 tacle scales long and flat, but on basal arm pores they are spine-hke 

 and out on arm they are very slender spinelets. Color (dried from 

 alcohol), yellow, yellowish, or white. 



Localities.— Albatross station 2859, off Alaska, lat. 55° 20' N.; long. 

 136° 20' W., 1,569 fathoms, gray ooze, bottom temperature 34.9°, 

 1 specimen; station 3603, Bering Sea, lat. 55° 23' N.; long. 170° 31' 

 W., 1,771 fathoms, blue ooze, bottom temperature 35.1°, 22 speci- 

 mens; station 4761, off Alaska, lat. 53° 57' 30" N.; long. 159° 31' W., 

 1,973 fathoms, blue clay, bottom temperature 35°, 258 specimens; 

 station 4766, Bering Sea, lat. 52° 38' N.; long. 174° 49' W., 1,766 

 fathoms, bottom ?, bottom temperature ?, 18 specimens. Bathy- 

 metrical range, 1,569 to 1,973 fathoms. Temperature range, 35.1° 

 to 34.9°. Two hundred and ninety-nine specimens. 



Ttjpe.— Cat. No. 25611, U.S.N.M., from station 4766. 



This seems to be a remarkably well-characterized species, confined 

 to very deep water in the vicinity of the Alaskan peninsula and islands. 

 Its nearest relative is probably leptodenia, but the form of the radial 

 shields, the much smaller and more numerous disk scales, the numer- 

 ous disk spinelets and the larger and better spaced oral papillae serve 



