OPIIirRA BREVICAUDA. 17 



one irregular in shape, longer than others ; pointed ; second one larger 

 than those beyond, irregular, flattened ; two innermost ones stout, coni- 

 cal ; the rest line, sharp, spine-like; teeth, five; lowest one sharp, coni- 

 cal ; second and third Hat, tapering; fourth Hat, with nearly a square 

 shape ; uppermost one like second and third ; mouth-shields triangular 

 heart-shaped, point inward, inner sides a little re-enteringly curved, cor- 

 ners strongly rounded, length to breadth, 1.9 : 2.2 ; side mouth-shields, 

 and space between mouth-shields and mouth-papilhi', covered by loose 

 granulation; under arm-])lates overlapping, about as long as broad; small 

 compared with the width of arm ; outer side curved, laterals re-enter- 

 ingly curved, inner laterals short and a little sloping, inner side shorter 

 tlian outer, and nearly straight ; length to breadth (twelfth plate), 

 1.2 : 1.2. First plate has a lobed outer side, in consequence of two 

 pores lying between it and second plates ; plates just within margin 

 of disk are, as usual, rather broader than those just beyond. The pro- 

 portions of the twelfth plate are continued in those beyond, till near 

 the end of the arm ; the plates, however, grow more shield-shaped, 

 and proportionately longer. Side arm-plates encroaching a little be- 

 tween both upper and under plates ; upper arm-plates broader than 

 long, thickened, somewhat irregular, sometimes broken, bounded with- 

 out and within by more or less wavy lines ; outer corners strongly 

 rounded ; inner side shorter than outer ; length to breadth (seventh 

 plate), 1.4 : 3.4 ; two thirds out on arm, same general shape ; length to 

 breadth, .9 : 1.8. First four plates enclosed by scaly prolongations of disk, 

 and accordingly modified in shape; first plate quite rudimentary; disk 

 entirely covered, except a few scales at base of arms, with compara- 

 tively coarse granulation, about thirty-six grains to a square mm. ; arm- 

 spines, nine, of nearly equal length, unusually short, stout, and thick ; 

 length near base of arm to length of under arm-plate, .7 : 1.2 ; the 

 spines are pointed, and but little flattened ; tentacle-scales ; inside one 

 long, oval ; length to that of under arm-plate, .7 : 1.2 ; outside one 

 shorter, broader, and cut off at its end ; color, in alcohol ; above, light 

 }'ellowish-brown, disk finely speckled with dull sap-green, arms irregu- 

 larly blotched and banded with the same ; below, ground-color same as 

 above, but lighter, on arms and mouth-shields some traces of green. 



Variations. — This species seems to fade in alcohol. It is then some- 

 times quite white ; but dry specimens preserve the colors, more or less. 

 These are various tints of sap-green, lake-red, and rusty-brown, much 

 blended, and irregularly disposed. A common pattern is a brown disk 

 above, greenish round the edges, upper surface of arms variously banded, 

 spotted, and mottled, with many shades of green and red; interbrachial 

 spaces, below^ greenish brown, speckled with red, a red spot on each 

 mouth-shield ; under surface of arms similar to upper surface, but more 



