Boone, Echinodermata, Cruises of "Eagle" and " Ara," 1921-28 123 



Color: Variable. One kind, recorded from living specimens by 

 Agassiz, had the abactinal surface of the central primary plate yellow, 

 the remainder of the surface vandyke brown with flecks of brown 

 and white, this color being continuous on the dorsal plates of the 

 arms, the later arm-plates yellow. On another specimen there was a 

 large, oblong patch of yellow in the center of the disk and a smaller, 

 round, yellow spot in each interbrachial space, all these spots being 

 limited by black flecks; the remainder of the disk is mottled with 

 brownish and greenish gray with black flecks; the dorsal arm-plates 

 are lighter or darker greenish gray and the lateral arm-plates bright 

 yellow, giving the effect of bands of color on the arms. 



Technical description : Disk diameter 18 mm., arm length 48 mm., 

 with the tip broken off. The abactinal surface is covered with flat, 

 regular, primary plates, each surrounded by a single line of 14 to 20 

 small, angular scales. The primary plates are very regularly arranged 

 in the following order : a rosette in the center, composed of six plates, 

 of which the central one is rounded and slightly smaller than the 

 surrounding five which are more angular; from this group there are 

 arranged five radiating interbrachial rows, each consisting of three 

 primary plates. In the interbrachial space there is one large primary 

 plate between the central rosette and the inner ends of the radial 

 shields. The radial shields are of moderate size, pear-seed shape, with 

 the points inwards, large, dilated; greatest width of the shield is 

 equal to two-thirds of their length; they are widely separated from 

 each other within by the projecting brachial primary plate, followed 

 by a large, belted scale and without margined by a broad wedge 

 formed of three scales, the outer two of which are quite large and 

 swollen. The outer, under interbrachial space is covered by three 

 large, swollen, triangular plates, and the actinal interbrachial space 

 by three transverse rows of smaller, irregular, flatfish plates. The 

 outer genital plate is enlarged and forms a prominent ridge. Mouth 

 papillae eleven, closely set in an even row, the outermost one elongated 

 and very acuminate, somewhat overlapping the adjacent one which 

 is nearly twice as wide as long and is the widest of the series; the 

 balance are squarish with beveled cutting edges, the innermost one 

 directed toward the mouth center. There are four teeth, regularly, 

 slightly decreasing in breadth from below upwards, the lower three 

 are broad, flat, with a curved cutting edge ; the uppermost one is 

 narrower and more acuminate. The mouth-shields are longer than 

 broad, 2 :1, with the outer side convex, the lateral side nearly straight, 



