OPHIURA APPRESSA. 35 



length to breadth, .9 : 1. The plates maintain the same shape till near 

 tlie point of the arm, Avhere the inner lateral sides ])egin to grow pro- 

 ])ortionatcly longer, and at the very tip the shape becomes almost tri- 

 angular. Side arm-plates very evenly em'ved, on their outer side 

 encroaching a little on upper arm-plates, so tliat their upper edges can 

 be well seen from above. Ujiper arm-])lates broader than long, bounded 

 without and Avithin by nearly straight lines (outer side sometimes a 

 little re-enteringly curved), sides well rounded, overlapped on their 

 inner portion by side arm-plates. First plate small, and partly covered 

 by fine scales which are at the base of the arm ; length to breadth, 

 .t; : 1.8 ; twelfth plate, length to breadth, 1 : 2.2. Al)out two thirds out 

 on arm, the plates begin to be more overlapped hy the side arm-plates, 

 avIhcIi makes the lateral sides more sloping, and inner side shorter, so 

 that, in the last three or four joints, the plates are triangular, the side 

 arm-plates meeting above. Inner pair of genital slits granulated ; outer 

 pair granulated on one side, and scaly on the other. Arm-spines com- 

 monly nine, short, flattened, tapering only near the point, which is 

 rounded ; of nearly equal length, except lowest one, Avhich is decidedly 

 longer, and does not taper at all ; lengths to that of lower arm-plate 

 (twelfth joint), lowest spine, .9:1; second, .7:1; third, .6:1; eighth 

 .5:1; second, third, and fourth joints, three spines ; two uppermost 

 much thinner ; fifth and sixth, five spines ; seventh and eighth, seven 

 spines ; ninth, eight spines ; two thirds out on arm there are six spines, 

 and at the very tip, only four. Granulation of disk very close, smooth, 

 and even, covering every part, except a few scales at base of arms, and 

 extending below quite to the mouth-papilh\3 ; grains remarkably round 

 and smooth, about 110 to a square 7nm. Two tentacle-scales ; inside one 

 longer, oblong, with rounded corners, length, .7°"°' ; outside one about 

 two thirds as long, somewhat broader, and cut off" square at the end. 

 Color, in alcohol : above, ground color yelloAvish white, with irregular 

 stripes and patches of greenish black on disk, and belts of the same on 

 arms ; the edges of the dark arm-plates are, however, speckled w^ith 

 lighter ; below, interbrachial spaces du-ty olive, wdth two large spots of 

 whitish in each ; chewing apparatus dirty white, ground color of arms 

 the same, marked and banded with different shades of brownish olive. 



Variations. — It is hard to find two specimens colored alike. There 

 are two chief varieties, the gray, which was that described originally by 

 Say, and the variegated green. The gray is more uniform, having 

 usually the disk greenish gray, wdth fine points of darker and lighter, 

 and the arms irregularly banded with darker, the lower parts being 

 similar, but lighter. The green variety may be marbled, spotted, and 

 lined with every possible pattern of green and whitish or yellowish ; 

 sometimes a specimen may be seen almost pure white. The gray va- 



