NORTH PACIFIC OPHIURANS IN NATIONAL MUSEUM CLARK. 153 



AMPHIURA PSILOPORA, new species.a 



Disk 4 mm. in diameter; arms about 20 mm. long. Disk covered 

 by comparatively few (180 to 200) large scales. Radial shields short, 

 rounded triangular, not twice as long as wide, widely separated prox- 

 imally but touching distally. Upper arm plates broadly triangular, 

 wider than long, scarcely in contact : distal margin very convex. 

 Interbrachial spaces below covered by about fifteen to twenty coarse 

 scales. Oral shields rounded distally and with a rounded point 

 proximally, somewhat longer than wide. Adoral plates very large, 

 triangular with a truncate angle where they touch the second under 

 arm plate, and a blunt angle where they touch each other, proximal to 

 the oral shield; oral plates also very large. Oral papilla?, two on a 

 side, one very large, thick, and rounded at apex of jaw, the other 



FIG. <>3. AMPHIURA PSILOPORA. x 12. a, FROM ABOVE; 6, FROM BELOW; c, SIDE VIEW OF THREE ARM 



JOINTS NEAR DISK. 



long, stout and spine-like at inner end of adoral plate; scale of first 

 oral tentacle pore conspicuous, broad, and truncate. Genital slits 

 small. First under arm plate tetragonal, wider within than distally; 

 succeeding plates somewhat hexagonal, longer than wide, more or less 

 broadly in contact. Side arm plates moderately large, not meeting 

 either above or below, at least near base of arm; each plate carries 

 four (or three on most joints) rather stout, terete spines, of which the 

 lowest is scarcely longer than the others and about equals the joint. 

 Tentacle pores large and wholly naked. Color (dried from alcohol), 

 yellowish-white. 



6f, signifying naked, and -bpoc, signifying a way through, a pore, in reference 

 to the absence of tentacle scales. 



