134 OPIIIOCNIDA HISPIDA. 



Description of a Specimen. — Diameter of disk, 9°"°- ; from outer 

 side of mouth-shield to outer corner of opposite mouth-sht, 3.3°"°' ; 

 width of arm without spines, 1.6""°- ; length of arm, 95"™' ; distance 

 from outer side of mouth-shield to inner points of mouth-papilla?, to 

 that between outer corners of mouth-slits, 1.5 : 1.5. Mouth-papilljB, 

 three on each side ; two outer ones like short, stout, conical, rounded 

 tubercles ; innermost one much the largest ; rounded, flattened, swollen ; 

 situated higher than the other two, and running upwards to the teeth ; 

 resembling a tooth-papilla. Teeth four, lowest one smallest, variable in 

 size, usually broader than long, very thick and rounded, sometimes sj^lit 

 in two ; second one longer than broad, very stout, nearly cylindrical ; 

 third tooth similar, but rather more flattened ; uppermost one longest, 

 stout, thick, flattened. Mouth-shields small, short, diamond-shaped, with 

 rounded angles, and sides sometimes straight and sometimes a little 

 curved ; length to breadth, .8 : .7. Side mouth-shields small, triangular, 

 somewhat variable, not meeting within. Under arm-^jlates very regu- 

 lar, squarish, broader than long, with lateral sides nearly straight, outer 

 and inner sides a little curved, and corners rounded ; first five or six 

 plates gradually increasing in size, but all of them smaller and propor- 

 tionately narrower than those beyond ; first plate larger than is usual 

 in allied species, corners quite rounded off; length to breadth, .2 : .4 ; 

 third plate a trifle wider without than Avithin, lateral sides a little re- 

 enteringly curved, inner side nearly straight ; length to breadth, .4 : .5 ; 

 twentieth plate typical ; length to breadth, .5 : .7. Side arm-plates 

 encroaching a little above, but not at all below, even at tip of arm. 

 Upper arm-plates much broader than long ; outer side nearly straight, 

 with a slight notch in the middle, lateral and inner sides curved, outer 

 corners cleanly rounded ; length to breadth (twentieth plate), .5 : 1.3. 

 Disk-scales rather thick for their size, largest near radial shields on the 

 centre of the upper surface, about 70 to a square mm. ; below, somewhat 

 smaller and more even. The scales are considerably obscured by a 

 pretty thick growth of short, slender, sharp thorns, about .2'°'°" long ; 

 they are everywhere, except on the radial shields, and a bare stripe 

 below, running along each genital slit ; the thorns are stouter near the 

 radial shields. Radial shields small, narrow, tapering inward, separated 

 by a strip of thorny scales ; length to breadth, 1.8 : .5. Arm-sj^ines 

 three, short, blunt, cylmdrical, a little tapering, of nearly equal lengths ; 

 lengths to that of under arm-plate (twelfth joint), .6, .6, .6 : .5. Tentacle- 

 scales two, wide, short, thin, with a curved free edge, standing at right 

 angles to each other, the inside one running along the lateral side of 

 the under arm-plate. Color, in alcohol : above, disk dull bluish-gray 

 (clay color) ; arms straw, with irregular bands and patches of black ; 

 below, interbrachial spaces same as upper surface ; mouth-parts nearly 

 white ; imder arm-plates brownish, fading to straw-color farther out on 



