94 



BULLETIN 75, UNITED STATES NATIONAL MUSEUM. 



pores of arm large, round, with a single, big, spinelike tentacle 

 scale on proximal side. Color (dried from alcohol), pale gray. 



Locality. — Albatross station 4765, Aleutian Islands, lat. 53° 12' N. ; 

 long. 171° 37' W., 1,217 fathoms, fine black sand, bottom temperature 

 35.2°, 8 specimens. 



Type.— Cut. No. 25534, U.S.N.M., from station 4765. 



The smallest specimen has the disk only about 3 mm. in diameter 

 but in practically all of its characters it agrees with the others, 

 except that there seems to be a well-developed second upper arm 

 plate, which is not present in the type specimen. There is no danger 

 that this species will be confused with any other ophiuran, even if 

 these specimens prove to be very immature. 



OPHIOTROCHUS LONGISPINUS, new species.a 



Disk 6 mm, in diameter; arms about 30 mm. long. Disk very 

 flat, thin, covered by radial shields and about twenty-six large 



plates (six primaries, five 

 other radials, and three 

 plates in each interra- 

 dius) regularly arranged 

 and surrounded by nu- 

 merous much smaller 

 scales; along margin of 

 disk are numerous small 

 granules. Radial shields 

 longer than broad, 

 rounded at both ends, 

 separated by a narrow 

 line of scales or barely 

 in contact. Upper arm 

 plates triangular, or tet- 

 ragonal with outer end 

 rounded, very minute 

 but apparently present 

 to very tip of arm. In- 

 terbrachial spaces below 

 C covered with scales, 



Fig. 33.— OPHIOTROCHUS longispinus. xs. a, from above; 6, wliich are more or less 



FROM below; c, side view of three arm joints near disk. 11 • n 



concealed, especially 

 near margin, by coarse granules. Oral shields not very large, triangular, 

 with outer corners more or less rounded. Adoral plates very long, 



a Longus, signifying long, and spinus, signifying spine, in reference to the very 

 long arm spines of the first joint. 



