Boone, Echinodermata, Cruises of "Ara'' and "Alva" 127 



Colour: The present specimens, which have been preserved 

 in alcohol for about five years, still have the radialia deep seaweed 

 green, lightly maculated with cream as is the center of the disk, 

 the remaining small plates are maculated with a (faded?) paler 

 green and cream. The dorsal surface of the arms is transversely 

 banded, having approximately every other plate dark green with 

 the adjacent plates lighter green maculated with cream. The 

 pattern in its entirety presents an indescribably beautiful mosaic 

 in tones of green and cream. 



Technical description: Disk diameter 4 millimeters, arm 

 length about 24 millimeters. Disk somewhat hexagonal with the 

 abactinal surface nearly covered by the six pairs of radialia, each 

 of which extend inward for three-fourths of the radius of the 

 disk ; the center is paved with numerous small irregular scales 

 and similar scales cover the interradial area and in a few instances 

 occur in a single linear series between the inner lateral margins 

 of the paired radialia. The radialia are long, narrow, each plate 

 being subtriangulate with the apex directed centerward; the 

 inner lateral margins lie side by side, or in certain instances are 

 separated slightly on the inner half by a linear series of scales ; 

 the outer margin is produced to a rounded peak at the angle adja- 

 cent to the paired plate. The actinal surface has the interradial 

 portions covered with small scales similar to those of the abactinal 

 surface. 



The central mouth shield is small, but very little larger than 

 the second under arm plate and is wider than deep, more heart- 

 shaped than suboval with the inner apex subacute. The side 

 mouth shields are somewhat triangular with the basal inner angle 

 thickened and applied to the outer half of the lateral margin of 

 the central plate, while the outer angle is more enlarged and 

 rounded and touches the inner margin of the under arm plate, 

 with the inner process of the side arm plate narrowed and applied 

 to the inner side margin of the central plate, with the inner ends 

 meeting. The mouth frame has the two halves separated proxi- 

 mally by a median cavity, but with the inner half with the adja- 

 cent margins meeting and distally supporting a large squarish 

 tooth. There are two smaller, well separated, squarish, mouth 

 papillae on each side of the mouth frame. 



There are consistently six arms present in each of the eighteen 

 specimens. The dorsal arm plate is wider than long, with the 



