83 



lengtli to breadth, .6 : .6. Upper arm-plates regular and ■well marked, 

 ranch wider than long, wider without than within, lateral corners un- 

 usually sharp ; outer side cleanly curved ; length to breadth, .6 : 1.2 : 

 their surface is closely covered with minute thorny spines, like those 

 of the disc, but smaller. Disc closely beset with short minute spines, 

 which are smooth on the sides, but have a crown of four to six thorns ; 

 the radial shields also are covered so as to look like the rest of the 

 disc ; below, the spines are smaller, more scattered, and more pointed. 

 Arm-spines very slender and elegant, tapering, pointed, uppermost 

 and lowest ones shortest ; on the basal joints, commonly eleven ; 

 lengths to that of under arm-plate, .6, 1, 1.4, 1.6, 1.6, 1.6, 1.6, 1.2, .9, 

 .6, .3 : .6. Tentacle-scale small and rounded. Color, in alcohol, 

 above, faint purplish-blue, arms banded with darker and a broken 

 stripe of the same running along the middle line ; interbrachial spaces 

 below, same as above, the rest lighter. 



Variations. In specimens that have the disc spines less closely set, 

 the disc is seen to be covered with thin, small, rounded scales ; the 

 outlines of the radial shields, also, may be seen. The uj)per arm- 

 plates are hexagonal, having the outer side in three lines. The arms 

 in some specimens attain a length twelve times that of the disc 

 diameter. 



Opldotlirix demessa has a very soft puffed disc, which commonly 

 wrinkles in alcohol ; it somewhat resembles O. longipeda and O. para- 

 sila, but has little thorny spines on the upper arm-plates, and is other- 

 wise distinguished. Sandwich Islands, Kingsmill Islands. 



Ophiothrix propixqua, Lj^man. 



Special marks. Disc sparsely granulated and covered above with 

 narrow scales, which form five to seven radiating rows in the inter- 

 brachial spaces. Radial shields naked. 



Description of a specimen. Diameter of disc 11 millim. Width of 

 arm, without spines, 1.6 millim. Length of arm, 125 millim. Tooth- 

 papillae standing nearly on a level with each other ; thirteen to fif- 

 teen, in horizontal rows of two, or more commonly three ; the lowest 

 one smallest. Teeth four, very .thick and stout, the highest one 

 smallest. Mouth-shields small, irregular oval, or oval heart-shaped, 

 broader than long; length to breadth .7 : 1.2. Side mouth-shields 

 short and wide, not meeting within. Under arm-plates oval, broader 

 than long, the outer side a little re-enteringly curved ; length to 

 breadth (12th plate) .6 : .8. Upper arm-plates pointed oval; much 

 broader than long ; length to breadth, .6 : 1.5. Disc covered above 

 with narrow, elongated, rather indistinct scales ; arranged In parallel, 

 radiating rows ; from five to seven such rows in each interbrachial 

 space ; and a single row, of three or four scales between each pair of 

 radial shields ; these scales bear a few rough grains ; outside each 



