THE OPIIIURIDiE. 



135 



triangular 



Disk covered with distinct, rather thick, smooth, polygonal scales, among 

 which the primary plates are not to be seen, except the pentagonal central 

 plate. Radial shields not quite so long as half the radius of the disk, twice 

 as long as broad. They are widely separated by a single row of scales. In 

 the interbrachial spaces there is a conspicuous marginal plate, separated from 

 the radial shields only by some very narrow scales. Under side of the disk 

 covered by similar polygonal plates. The edge of the disk not sharp, both 

 sides rounding towards each other. Genital scales distinct, but not very 

 wide ; genital slit reaching to the margin of the disk ; its inner end, at the 

 outer end of the mouth shield, is somewhat widened ; here is seen a little 



opening. Papilla along the genital slits distinct, close set, 

 rounded. They do not extend to the dorsal side of the arm, there being no 



arm-comb. 



Five (four-six) short, equal arm-spines, the two or three lowest a little 



closer together than the others. Only the first three joints with tentacle 



pores, each pore with one large oval tentacle scale at the outer side. 



Color in alcohol : gray. 



1 specimen from Station 3404, 385 f. 



From the same station there is another specimen (diameter of disk 5 mm.), 

 which differs from that described, the disk scales being somewhat granu- 

 lated, and the radial shields not being quite separated. There are four arm- 

 spines; the. ventral plates are separated from the third. Evidently it is a 

 younger stage of the same species. 



21. Ophiomusium variabile n. sp 



Plate IV. Figs. 4-6. 



Diameter of disk, 14 mm.; width of arms close to disk, 2.5 mm.; length 

 of arms, c. 5 times the diameter of the disk. Seven close set square mouth 

 papilla? on each side, one longer, pointed at apex of jaw ; the three outer 

 ones are much broader and larger than the inner ones. Mouth shield a 

 little longer than broad, of a curious form; an acute angle within, then 

 widening, with the sides rounded ; the outer part very restricted ; the whole 

 looks like a leaf with its stalk. Side mouth shields long, their inner end 

 very narrow, restricted by the mouth shield, just meeting within or sepa- 

 rated ; their outer end is very broad. 



I. 

 i 



