328 BULLETIN OF THE 



Opbiochonclrus couvolutus Lyman, sp. nov. 



ial Maries. — Six nearly equal, rounded, tapering arm-spines. Ra- 

 dial shields twice as long as wide and considerably separated. Seven 

 mouth-papillae. One tentacle scale. 



1 >■ icription of a Specimen. — Diameter of disk 7.5 mm. Length of arm 

 24 mm. Mouth-papilla 1 seven, all short, stout, and flattened ; the two outer 

 ones on each side squarish ; the third more tapering, like a blunt tooth ; 

 the innermost one lying just under the teeth, and similar to them, except 

 that it is more pointed. Teeth four, flat, squarish, with a cutting edge a 

 little curved at its corners. Mouth-shields broader than long, rounded 

 heart-shape ; length to breadth .8 : 1.2. Side mouth-shields large and 

 stout, meeting closely within : wider without, where they are soldered to the 

 first side arm-plates. Underarm-plates wide oval, with a slightly re-enter- 

 ing curve without, strongly separated by the side arm-plates; length to 

 breadth (Cth joint) .5 : 1. Side arm-plates large, thick and swollen, not 

 joined above, but meeting below, even at the base of the arm, where they 

 are so soldered together that their line of juncture cannot be seen; their 

 surface is rough, contrasting with that of upper and under plates, which is 

 smooth. Upper arm-plates broad fan-shape, with the wide curved side 

 outward ; the two lateral sides are straight, and converge to the inner side, 

 which is very short ; the first upper plate is more or less covered by the 

 encroachment of the disk; length to breadth (3d plate) 1 : 1.4. Three 

 fourths out on the arm the upper plate is long wedge-shaped, with a curved 

 outer side; this shape is determined by the juncture above of the side 

 arm-plates. Interbrachial spaces below, and upper surface of disk, except 

 radial shields, closely granulated with minute, rough, nearly equal grains, 

 about 150 to a square mm. Radial shields widely separated ; long oval, 

 wider without than within : length to breadth, 2 : 1. The disk rises well 

 above the arms, on which it encroaches somewhat by growing out on them 

 in a sloping direction, as is often seen in Ophiura. Over the arm there is a 

 slight irregular notch in the disk. Arm-spines short, rounded, tapering, 

 moderately stout, nearly equal ; second one from top a little the longest ; 

 lowest one somewhat the shortest. Second joint, two spines; third joint, 

 three; sixth joint, six; lengths to that of the under arm-plate, .6, .7, .6, 

 .6, .6, .5 : .5. At the very tip of the arm the under spine becomes some- 

 what hooked on its side and end. Tentacle scale, one, small, short, and 

 tooth-like. 



Color, in alcohol, light yellow. 



Variations. — A small specimen brought up in the same cast is supposed 

 to be the young of this species. Disk 2 mm. Arms 1G mm. The upper 

 surface of the disk is entirely occupied by the eight radial shields, which 

 are lu-oad wedge-shape, and have the outer side bevelled, so as to make a 



