NORTH PACIFIC OPHIURANS IN NATIONAL MUSEUM- 



7L.ABK. 



89 



OPHIURA POMPHOPHORA, new species. & 



Disk 15 mm. in diameter; arms about 45 mm. long. Disk convex, 

 but only moderately high at margin, covered by about forty plates, 

 each of which is more or less convex, the six primary plates most so. 

 Radial shields longer than wide, joined for about half their length, 

 but well separated proximally by a large diamond-shaped plate. 

 Arms rather wide at base, somewhat depressed, very flat orally, and 

 becoming flat dorsally near tip. Upper arm plates convex or some- 

 what swollen, only first six or seven in contact; first two plates 

 rounded tetragonal, very 

 much wider than long; next 

 three or four plates also tet- 

 ragonal, and wider than 

 long, but distal margin very 

 much longer than proximal ; 

 succeeding plates triangular, 

 slightly wider than long. 

 Interbrachial spaces below 

 narrow, covered by huge 

 oral shields, and single mar- 

 ginal plates, between which 

 are two or three small tri- 

 angular plates; all these 

 plates are notably thick and 

 heavy, even if not exactly 

 convex. Oral shields long 

 triangular, longer than wide, 

 rounded distally and pointed 

 within. Adoral plates and 

 oral plates distinct, moder- 

 ate, slightly convex. Oral 

 papillae three or four on a 

 side, outer ones very wide and truncate; an infradental papilla 

 present at apex of jaw. Genital slits long and conspicuous; each 

 genital scale with about twenty-five marginal papillae, which are 

 truncate and crowded orally, but become rounded at tip or bluntly 

 pointed at upper end of genital scales; arm comb thus formed, 

 directly continued by a series of four or five small papillae on 

 outer end of radial shields; the two series on opposite sides do not 

 quite meet, however, across base of arm. First under arm plate 

 octagonal, about as long as wide; second, larger, more tetragonal 



FIG. 29. OPHIURA POMPHOPHORA, ADULT. X3.5 a, FROM 

 ABOVE; 6, FROM BELOW; c, SIDE VIEW OF THREE ARM 



JOINTS NEAR DISK. 



& /7o ( <6f , signifying bubble, and <f>opa, signifying carrying, in reference to the convex 

 disk plates. 



