AMrimijA uirncA. 



129 



ano-lc (lircctGcl inward ; outer anulo truncated, and maklno; a sliulit 

 })eak ; other an^u'les ^^liglltly rounded ; length to Ijreadth, .0 : .5. Side 

 mouth-shields not meeting within, Up[)er arm-plates irregular oval, 

 outer side less curved than inner side; length t<j l)ieadth, f):.7. Under 

 arin-])lates scarcely touching each other ; inner one live-sided, the rest 

 nearly square, with a strong notch in the outer side ; length to breadth, 

 .4 : .4. Scales of disk fine and even, about 140 to a square mm. ; some 

 of those near margin of disk bearing very fine prickles on their edges. 

 Primary jdates not conspicuous. Kadial shields elongated oval, tapering 

 within, joined for their whole length ; length to breadth, 1 : .5. Arm- 

 spines three, about as long as the joints, delicate, sharp, regularly 

 tapering. Tentacle-scales two, both of them small and delicate. Color, 

 in alcohol : ni)per and under surface of disk dark greenish-gray, with a 

 margin of light ; arms light straw-color. 



Variations. — The mouth-shields vary in shape to an unusual degree ; 

 sometimes they have a strong peak without, and again none at all ; 

 they may be nearly rectangular, or almost oval, and some are not far 

 from round. The under arm-plates may be more or less pentagonal ; 

 but, in the adult, most of them are nearly square. The young, with a 

 disk 2.5""" in diameter, have the under arm-plate.^ pentagonal, with a 

 deep notch in their outer side, and separated by the side arin-plates ; 

 they have also, on the back of the disk, a conspicuous rosette of round 

 primary scales. 



This species differs from A. occidentalis in its notched under arm- 

 plates, sharp spines, and prickly scales of the disk. It is a somewhat 

 aberrant species, and by its prickly scales approaches Ophiocnida sca- 

 briuscida. 



LIST OF SPECIMENS. 



17 



