426 PROCEEDINGS OF THE NATIONAL 3IUSEUM. vol.40. 



marginals. Fourteenth actinolateral spine the longest. R = 36 mm., 

 r = 22 mm., 11 = 1.64 r. Breadth of ray, over all, 21 to 25 mm.; of 

 paxillar area alone, 17 to 21 mm. 



Description. — The paxillar area is sharply defined from the lateral 

 fringe, or actinolateral membrane, which is interradially deeply 

 indented and follows the contour of the raised supradorsal membrane. 

 Thus the actinolateral membrane forms a narrow border of nearly 

 uniform width, and the spines do not project beyond the edge. They 

 are clearly visible as the membrane is translucent. The supradorsal 

 membrane is thin and translucent, without visible muscle-fibres, and 

 with small rather widely spaced inconspicuous spiracula, which are 

 not in definite areas, but sometimes form irregular lines. With the 

 exception of an interradial area they are pretty uniformly distributed 

 all over the membrane. Membrane everywhere rough with the points 

 of the paxillar spinelets, of which there are usually 5 (laterally some- 

 times 7) to a paxilla. The latter are in 9 quincuncial longitudinal 

 series. Each paxilla springs from a cruciform or 4-lobed base, the 

 lobes overlapping those of 4 other plates leaving quadrate or lozenge- 

 shaped papular areas. The pedicels are longest on the lateral paxilla? ; 

 those of midradial series about half as long as the laterals, and the 

 spines, which are webbed, are in all cases longer than the pedicels. 

 One spine is usually longer and stouter than the others. The spines 

 are three-edged or triradiate in cross section. The papulae (1 to 

 an area) are attached to the pedicels. The valves guarding the oscu- 

 lum have a truncate summit and are strengthened by about 12 spines, 

 of which the 5 or 6 median are longest. About 8 other spines, much 

 shorter, form a comb just back of the valves, and are attached to the 

 same pedicel. The membrane at the base of the fans is pierced by 

 scattered spiracula, and that between the fans has numerous spiracula 

 in short irregular lines. The supradorsal membrane is dotted with 

 numerous very small whitish spots of unequal size, due probably to 

 groups of gland cells. There are rather large well-spaced brownish 

 rings or spots on the outer half of R. 



Ambulacral furrow wide; tube feet, with small disks, in 4 

 longitudinal series. Adambulacral plates of two sorts, prominent 

 and nonprominent. The former project farther into furrow and 

 bear an oblique transverse series of 3 slender spines invested in 

 membrane which forms a small sacculus at tip. The outer spine 

 is the longest (equals the length of 5 plates at base of furrow), the 

 other two decreasing slightly in length. The innermost often pro- 

 jects between 2 feet of the outermost series. The nonprominent 

 plate corresponds to a tube foot of the outermost series, is set back 

 slightly, and bears only 1 spine, which stands in the same longi- 

 tudinal series (with reference to long axis of ray) with the outer- 

 most spine of the prominent plates, and is of about the same length 



