199 



Outer edge of mouth-shield to outer corner of opposite mouth- 

 sht, 12 miUim. Width of arm, without spines, 7 millim. Length 

 of arm, 133 milHra. Mouth-papillae, about 18 to each angle of 

 mouth, small, tooth-like, somewhat crowded, the innermost, and 

 the outermost but one, on each side, broader and larger than their 

 neighbors. Teeth broad, flat, short, with the free edge curved, 

 the upper ones more pointed. Mouth-shields very broad heart- 

 shape, usually presenting three rounded lobes, of which one is 

 directed inward ; length to breadth, 2.5 : 3.5. Side mouth-shields 

 covered by granulation of disc. Under arm-plates small, squar- 

 ish, bounded without by three sides, with much rounded angles, 

 and within by a slightly curved line; length to breadth, (13th 

 plate,) 1.5 : 2. The first five plates are smaller and narrower ; 

 and, between the 1st and 2d, 2d and 3d, and 3d and 4th, there is 

 a pair of pores. Upper arm-plates very short and wide ; length 

 to breadth, 1.7 : 6.5. All the plates, except those just at the tip 

 of the arm, are broken in irregular pieces ; those near base of 

 arm usually in 5 ; those near its tip, in 3, or 4 ; so that the upper 

 surface seems covered with an irregular mosaic. Granulation of 

 disc fine and even, covering radial shields and the whole disc, 

 above and below ; near base of arms, above, are sometimes one or 

 two little naked plates of variable size. Arm-spines short, flat, 

 tapering, rather stout, nine in number ; three lowest ones rather 

 longer than the rest, and lowest one longest of all ; upper ones about 

 half as long as side arm-plates. Two tentacle-scales, longer than 

 broad, flattened, outside one rather shorter and cut off more 

 square at the end. Color, in alcohol: above, purplish brown, 

 with upper arm-plates closely speckled with lighter ; below, chew- 

 ing apparatus, lowest arm-spines, and under arm-plates yellowish 

 white ; the rest purplish brown. 



Variations. The mouth-shields may differ somewhat in shape ; 

 and the under arm-plates may be light brown. 



This species at once strikes the eye by its short, rounded arms, 

 covered above by a multitude of irregular pieces. It is distin- 

 guished from 0. Panamensis, by broken arm-plates, proportion- 

 ately shorter arms, and absence of radial shields ; from 0. varie- 

 gata, by proportionately shorter arms, granulated side mouth- 

 shields, &c. It most resembles the dark variety of 0. cinerea 

 ( 0. AntiUariim, Ltk.) of the West Indies, but differs in having 

 shorter arms and covered radial shields. 



