258 Verrill, JVotes on Radiata. 



small ones ; the central one is largest, nearly circular, surrounded by 

 a rosette of several circles of plates, from which a band of three rows 

 of plates radiates to each interbi-anchial margin, and a less regluar row 

 to the base of each arm between the radial shields ; these are longer 

 than broad, pointed at each end, irregular, placed obliquely, and widely 

 separated at the outer edges, which are bordered next to the base of 

 the arms by a large convex plate. The upper arm-plates are quite 

 regular, with nearly straight outer and inner edges, widest outwardly, 

 with slightly concave, diverging sides ; near the ends of the arms 

 they become fan-shaped, and the side-plates meet above. Near the 

 base of the arms there are five very short arm-spines, of which the 

 lowest two are slightly longer than the others. 



Color, in alcohol, umber-brown above, with slightly indicated bands 

 of lighter brown toward the ends of the arms ; below uniformly 

 brown, of a somewhat lighter shade. Young specimens are lighter 

 colored, especially beneath. In another specimen the disk is grayish 

 yellow ; upper side of arms the same, with transverse bands of 

 brownish, occupying two or three plates, and an interrupted light 

 stripe, bordered with brown along the middle, formed by a spot of 

 yellowish white on the outer edge of each plate. All the upper plates 

 are mottled with lighter and darker yellowish brown. The upper 

 edge of the side-plates also has a light spot. Beneath uniform yel- 

 lowish white. 



OphiOCOma aethiops Llitken, Addit. hist. Oph., p. 145 ; Lyman, op. cit, p. 78. 



Very abundant at Panama and Pearl Islands, from whence Mr. 

 Bradley has sent about one hundred and fifty specimens. From La 

 Union he has also sent numerous large examples. It occurs also at 

 Acapulco (Coll. Mus. Comp. Zoology), and Cape St. Lucas (Smith- 

 sonian Institution). 



This species grows to a large size, many of our specimens measur- 

 ing 8 inches in length of arms ; 1 vS in diameter of disk ; arms, not 

 including spines, '3 wide; spines '3 long. 



It is allied to 0. eehinata and 0. Riisei of Aspinwall and the West 

 Indies, but differs in the shape and proportions of the arm-spines and 

 mouth-shields, as well as by having flatter arms, etc. In O. eehinata 

 the upper ai'm-spines are short, blunt, and remarkably thickened ; in 

 O. Hiisei they are long and slender, like the rest, but considerably 

 longer ; in the present species they are stout, the lower ones shorter, 

 and somewhat flattened, the upper ones becoming longer and stouter, 

 the uppermost being considerably thickened. In 0. eehinata the 

 mouth-shields are squarish, with rounded corners ; in 0. Hiisei they 



