104 BULLETIN 75, UNITED STATES NATIONAL MUSEUM. 



53 59' 11" N.; long. 166 25' 9" W., 45 fathoms, fine sand, mud, bot- 

 tom temperature 43, 2 specimens; station 3313, Bering Sea, lat. 54 

 1' 51" N. ; long. 166 27' 38" W., 68 fathoms, fine black sand, bottom 

 temperature 42.7, 1 specimen; station 3483, Bering Sea, lat. 57 18' 

 N.; long. 171 18' W., 56 fathoms, green mud, bottom temperature 

 36.8, 1 specimen; station 3609, Bering Sea, lat. 55 35' N. ; long. 168 

 20' W., 74 fathoms, green mud, sand, bottom temperature 37.9, 3 

 specimens; station 4812, Sea of Japan, lat. 38 31' N.; long. 138 40' 

 E., 176 to 200 fathoms, fine brown mud, bottom temperature 34.9, 2 

 specimens; Captains Harbor, Unalaska, 9 to 14 fathoms, 4 specimens; 

 Port Etches, Alaska, 12 to 18 fathoms, 3 specimens; between Icy Cape 

 and Cape Lisburne, 1 specimen. Bathymetrical range, 9 to 225 fath- 

 oms. Temperature range, 43 to 34.9. Twenty-one specimens. 



Type. Cat. No. 25540, U.S.N.M., from station 3312. 



A very interesting feature of this curious little, brittle star is the 

 way in which the radial shields become concealed with advancing age. 

 It is only in the largest specimen that they are completely covered, 

 and in many specimens they are conspicuous. There is also much 

 diversity in the distinctness of the five primary radial plates which in 

 some specimens are very noticeable. In the smallest specimen, which 

 is 6 mm. across the disk, the six primary plates, the radial shields, and 

 the interradial marginal plates are all very conspicuous. 



OPHIOPENIA TETRACANTHA, new species.a 



Disk 6 mm. in diameter; arms nearly 10 mm. long. Disk pentago- 

 nal, flat or somewhat elevated, covered with round, swollen, granule- 

 like plates among which the flat primary plates, radial shields and 

 marginal plates are usually conspicuous; a second interradial plate 

 and three plates in a longitudinal series between the radial shields of 

 each pair may also be distinguished in many specimens. Radial 

 shields very narrow and often more or less concealed. Upper arm 

 plates somewhat swollen, transversely oval, well separated; granular 

 scales of disk do not extend out around the arm plates; toward tip of 

 arm, plates become triangular. Interbrachial spaces below covered 

 by a scaling similar to that of disk. Genital slits very minute, cres- 

 centic, at each inner corner of first side arm plates; genital scales 

 concealed. Oral shields transversely oval, small. Adoral plates 

 squarish, each one nearly as large as oral shield. Oral plates ill 

 defined but with a knob-like swelling on proximal end. Oral papillae 

 small, ill defined and of variable shape, probably two on each side 

 and perhaps an unpaired one at apex of jaw. First under arm plate 

 somewhat pentagonal, about as wide as long; succeeding plates 



a Te-cpa (combining form of reaoapef}, signify ing four, and arcavda, signifying spine, 

 in reference to the number of arm spines. 



