NORTH PACIFIC OPHIURANS IN NATIONAL MUSEUM — CLARK. 185 



center of the disk and fewest near the radial shields. Kadial shields 

 very small, widely separated, only the distal ends visible, and these 

 are hardly distinofuishable fiom the laio:er disk scales. Upper arm 

 plates pentagonal or bell-shaped, wider than long, well separated 

 from each other or the basal ones barely in contact. Interbrachial 

 spaces below covered with small scales. Genital slits rather small. 

 Oral shields wider than long, somewdiat i4iombic but with distal half 

 larger than proximal. Adoral plates large, much wider without than 

 within where they meet; oral plates small. Oral papillae six or seven 

 on a side, subequal, pointed; an unpaired one somewhat larger at 

 apex of jaw. First under arm plate small, squarish; succeeding 

 plates two or three times as wide as long, convex distally and with 

 more or less of a proximal angle, well separated from each other. 

 Side arm plates large, meeting above and below; each one carries six 

 slender, sharp arm spines, all more or less thorny, but the uppermost 

 nearly smooth. Tentacle scales two on the first pore of the arm, 

 sometimes on the second also, but single thereafter; at first rather 

 large and oval, they quickly become small and pointed and often 

 quite thorny near tip. Color (dried from alcohol), light brown. 



Localities.— Albatross station 4901, Eastern Sea, lat. 32° 30' 10" N. ; 

 long. 128° 34' 40" E., 139 fathoms, gray sand, broken shells, 1 speci- 

 men; station 4933, Eastern Sea, lat. 30° 59' N.; long. 130° 29' 50" E., 

 152 fathoms, rocky, bottom temperature 56°, 22 specimens; station 

 4934, Eastern Sea, lat. 30° 58' 30" N.; long. 130° 32' E., 103 to 152 

 fathoms, rocky, 18 specimens. 



Type.— Cat. No. 25608, U.S.N.M., from station 4933. 



The appearance of the radial shields inclines one to put this species 

 in Ophiacantha, but the general character of the arms and mouth 

 parts has induced me to consider it more nearly related to Ophiomitra. 

 The tentacle scales seem small compared with those of most species 

 of Ophiomitra, and this character, combined with the small radial 

 shields and characteristic disk spines, makes it easy to recognize the 

 species, even in the face of some little individual diversity in these and 

 other points. 



OPHIOMITRA BYTHIASPIS, new species.a 



Disk 12 mm. in diameter; arms about 60 to 70 mm. long, probably. 

 Disk divided by deep interradial sulci into five wedge-shaped parts, 

 each of which is subdivided by the narrow, deeply sunken radial 

 shields into three nearly equal portions; disk covering consists of 

 numerous irregular plates, smallest at center and largest near mar- 

 gins; many of these plates carry each a low, smooth, blunt, cylindrical 

 stump. Radial shields about four times as long as ,wide, slightly 



1 Bijdwc, signifying sunken and dazli', signif j'ing shield, in reference to the sunken 

 radial shields. 



