253 



cided peak inward; length to breadth, 1.3:1.8. Side mouth- 

 shields rather narrower than is common in the genus ; meeting 

 within. Under arm-plates much broader than long, hexagonal, 

 with angles more or less rounded ; first four plates smaller than 

 those beyond, and much more rounded ; most of the plates on the 

 first third of the arm are hexagonal, with pretty acute angles; 

 their outer side sometimes a little reenteringly curved ; length to 

 breadth, (12th plate,) .7 : 1.2. Upper arm-plates diamond- 

 shaped, with inner angle truncated ; lateral ones usually acute, 

 and outer one more or less rounded ; on the median line a ridse. 

 Length to breadth, (5th plate,) .7 : 1.3. Brachial and inter- 

 brachial rays of disc closely beset with stout spines of several 

 sizes, most of them long : the longest, 1.7 millim., the shortest, .3 

 millim. There seem to be no such short spines, bearing a crown 

 of slender thorns and remaining permanently small, as in 0. spic- 

 vlata, but the smaller spines seem only partly-grown large 

 ones ; the largest are stout and round, and have rows of five or 

 six thorns on their sides ; they usually end in three blunt thorns ; 

 the smaller ones are usually very thick at the base, but above the 

 first thorn grow suddenly smaller, and taper to a somewhat blunt, 

 thorny end ; they have rows of three or four thorns on their 

 sides ; the smallest spines are little stout cylinders, ending in a 

 conical clump of nine or ten short thorns ; rarely this clump has 

 an even top, and not more than six thorns. Radial shields nearly 

 bare, with only a few spines on their sides and inner ends ; 

 outer ends touching each other; length to breadth, 3.2:1.6. 

 Spines on interbrachial spaces below more slender and scattered, 

 not extending quite to the mouth-shields. Arm-spines rounded 

 and stout at their base, tapering regularly to a blunt point ; but 

 little flattened; ending in a crown of short, blunt thorns; 13th 

 joint, 8 spines ; lengths to that of under arm-plate, 3.5, 2.2, 2.5, 2.5, 

 1.8, 1.5, 1, .6 : .7. Upper spine always longest and stoutest, with 

 rows of about twenty-four small thorns on its sides ; it sometimes 

 attains a length of 4.5 millim. Tentacle-scales usually much 

 larger than are commonly found in the genus. Color, in alcohol : 

 above, disc dull cobalt blue, approaching lead color ; radial 

 shields lighter, with several large dark spots ; upper arm-plates 

 pale bluish, with a darker spot on each side ; arm-spines dark 

 at tips ; below, interbrachial spaces similar to upper surface ; 



