Boone, Echinodermata, Cruises of "Ara" and "Alva" 125 



Distribution : This species is apparently quite rare, the type 

 locality being the only published record of its occurrence. The 

 "Alva" specimen from Ingham Island, Queensland, substantially 

 extends the southern range of this species. 



Material examined: Three specimens, taken from coral, 

 Ingham Island, Queensland, October 12, 1931. 



Technical description : The disk diameter is 5 millimeters ; 

 the arm is 21 millimeters long and is very tapered distally. The 

 abactinal surface of the disk is of rounded-pentagonal contour and 

 is paved with numerous small overlapping scales. In the center 

 there is a rosette pattern composed of a small, circular, central 

 elevated scale, surrounded by about seven of the low small scales, 

 which in turn are surrounded by more small scales, which are 

 interspersed between five separated elevated subcircular scales 

 like the central scale and forming an interrupted circle around 

 it. Beyond these five large scales there are in longitudinal series, 

 one series on each brachial area, four similar coarse circular 

 scales, the outer two of which lie between the radial plates. Inter- 

 spersed among these and also covering the remainder of the 

 abactinal surface, the side margins of the interbrachial areas and 

 the interbrachial areas of the actinal surface is a pavement com- 

 posed of small subcircular, semicircular and irregular overlapping 

 scales. The paired radial plates are well separated, irregularly 

 oval, with the long diameter not more than twice the short diam- 

 eter, which is about equal to the center disk scale and also about 

 equal to the width of the space between the two radial plates of 

 a pair. 



On the actinal surface the scales are more even, smaller, con- 

 tinuously overlapping and extend up close to the jaw angle. The 

 genital slits are of moderate size. The central mouth plate is 

 slightly longer than wide, with the inner angle acute, the others 

 rounded. The side mouth shield is tapered to a very narrow apex 

 inward, this reaching to about half-way the length of the inner 

 half of the central plate and being produced to a wider externally 

 rounded lobe where the side mouth shield touches the first ventral 

 arm plate. The jaws are triangular, with six mouth papillae on 

 each side, these are coarse, of irregular shape and blunt distally 

 except the apical tooth, which is pointed. 



The arms are from four and one-half to six times the length 

 of the disk diameter. The dorsal arm plate is nearly triangular 



