﻿54 OPHIOCTEN KROYERI. 



great encroachment of the side arm-plates ; bomided without by a 

 gentle curve, and within by two lines a little re-enteringly curved, and 

 converging on the middle line in a sUght peak ; length to breadth 

 (sixth plate), .3:1; sometimes the inner side is bounded by an almost 

 straight line ; first plate longer than those beyond, broad triangular, 

 with angles rounded, and one of them directed inward ; length to 

 breadth, .7 : .8 ; second plate of nearly the same shape, but shorter and 

 more rounded. Side arm-plates encroaching below to an unusual 

 degree, so that, at the sixth jomt, the length of the line of juncture of 

 the side arm-plates, is to the length of the under arm-plate as .4 : .3 ; 

 near the end of the arm, almost the whole under surface is occupied by 

 the side arm-plates, the uiader arm-plates being reduced to little semi- 

 circular scales. Upper arm-plates regular, broader than long, narrower 

 within than without, bomided on outer, inner, and lateral sides by 

 straight lines ; length to breadth (fourth plate), .7 : 1.4. Disk plates 

 and grains : above, remarkably flat, and closely soldered together, so 

 that their outhnes are hard to see ; below, the scales are larger, more 

 swollen, and easily distinguishable ; in the centre, above, there is a 

 rosette of six large, round, separated primary plates, the largest having 

 a diameter of about 1°™ ; there are also a few other smaller primary 

 plates m the brachial and interbrachial spaces ; of the disk granules 

 there are about 60 to a square mm. Radial shields longer than broad, 

 widely separated, irregular, swelled and rounded without ; length to 

 breadth, 1.2 : .8. There is a continuous Ime of short, pointed papillae, 

 running along the genital slit, and passing along the edge of the disk, 

 over the top of the arm ; of these, those along the genital slits are the 

 most slender ; the stoutest papillas are those standing just over the arm, 

 on the sides, about five in number, and having a length of .2"'° ; the 

 four or five lying over the arm, on the middle line, are smaller, and 

 stand a little lower ; the first, second, third, and sometimes fourth, 

 upper arm-plates have papillse along their outer side ; of these the first 

 plate has the longest. Arm-spines three, rounded, tapering, very sharp ; 

 two upper ones much the longest ; lengths to that of under arm-plate 

 (sixth joint), 1.1, .9, .5 : .3. Tentacle-scale triangular, as broad as long, 

 with an angle outward ; on the first three or four joints an additional 

 scale on the outside of the pore. Color, in alcohol, light gray. 



Variations. — A specimen with a disk 11.5""°' in diameter had arms 

 about 36°""" long ; the color, in alcohol, was brownish white ; there were 

 ten or eleven mouth-papillse, the outer broad one Taeing broken in two 

 or three. The species grows as large as 15'""" for the diameter of the 

 disk. It has been taken at Spitzbergen (Professor Kroyer), and on the 

 coast of Greenland, in fifteen to twenty fathoms water, muddy bottom 

 (Barrett). 



