NOKTH PACIFIC OPHIURANS IN NATIONAL MUSEUM CLARK. 113 



peculiar oral shields and the three pairs of tentacle pores. The 

 smallest specimen (10 mm. across the disk) differs from the large 

 only in having the primary plates of the disk distinguishable and 

 in there being only two arm spines on many of the joints. As my 

 description and figures of this species were prepared before the publi- 

 cation of McClendon's paper, and as they are taken from much larger 

 specimens, it has seemed best to let them stand. 



OPHIOMUSIUM MULTISPINUM, new species.a 



Disk 40 mm. in diameter; arms about 240 mm. long. Disk flat, 

 thin, pentagonal or rather decagonal, owing to great size of radial 

 shields, covered with numerous, irregular, rounded, small plates more 

 or less embedded in the skin, and five pairs of huge radial shields; the 

 latter are about 14 mm. long by 6 mm. wide, but their inner ends are 

 more or less buried in the scale-bearing skin; they are widely sepa- 

 rated throughout their length. Upper arm plates persistent to tip 

 of arm; basal ones somewhat pentagonal, wider than long, but from 



FIG. 42. OPHIOMUSIUM MULTISPINUM. Xl-25. a, FROM ABOVE; 6, FKOM BELOW; c, SIDE VIEW OF THREE 



ARM JOINTS NEAR DISK. 



about fourth on they become diamond-shaped and as a rule are 

 longer than wide; they are in contact, or nearly so, to about the 

 eleventh plate. Interbrachial spaces below covered by numerous 

 rounded scales like those of disk. Oral shields arrowhead-shaped, 

 nearly as wide as long. Adoral plates long, wider without than 

 within; oral plates large, somewhat swollen proximally. Oral papillae 

 numerous, nine or ten on a side, outermost much the biggest. Gen- 

 ital slits moderate, about equal to three joints; genital scales long and 

 rather conspicuous. First under arm plate pentagonal, twice as 

 wide as long; next three similar, but longer; succeeding plates small, 

 triangular, persistent to end of arm. Side arm plates moderate, 

 little swollen, meeting broadly above and below except at extreme 

 base of arm; each plate carries twelve to sixteen very slender, 

 closely crowded, pointed spines, hardly one-fourth as long as side arm 

 plate; lowest spine (or two) often much stouter and more conspicu- 



o Multus, signifying many, and spinus, signifying spine, in reference to the numerous 

 arm spines. 



34916 Bull. 7511 8 



