464 BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 



and in having 2 acicular suboral spines to each plate (instead of 1 

 resembling an aperture papilla). Marginal contour pentagonal; 

 E=82 mm., r=55 mm.; breadth of paxillar area at base, 35 mm.; 

 distance from center of disk to margin of paxillar area on interradial 

 line, 30 to 32 mm. 



Description. — General appearance of abactmal surface very similar 

 to that of H. nohilis, the paxillar areas being raised above the level 

 of the very fleshy lateral membrane, and paxillae usually with 3 

 spines oriented as in nohilis. But there are 7 series of paxillae, 

 instead of 6, to each ray, and in proportion to the 2 lateral, or outer, 

 series of each side, the radial and either adradial are smaller than in 

 n-ohilis. In rhodopeplus the paxillae of the 3 median series are 

 abruptly smaller than the marginal paxillae, while in nohilis the 

 paxillae are nearly uniform in size so far as outward appearance is 

 concerned; at least there is no sharp break. Pedicel of superomar- 

 ginal paxillae near base of ray 3 mm. long, spines 7 mm.; pedicel 

 of radial paxilla, 1.75 mm., longest spine 6 mm., shortest 3.5 mm. 

 The 3 spines are usually unequal on the radial and adradial paxillae, 

 sometimes but much less often also on the marginal. Supradorsal 

 membrane rather thin, but thicker between the spines of a paxilla 

 than between the paxillae. Spiracula in lines around the paxillae 

 but never among the spines of a paxilla, these lines meandering and 

 joining to form an irregular meshwork. Extending laterally upon 

 the interradial membrane from margin of paxillar area are about 

 15 to 20 linear spiracular tracts, such as occur in nohilis, the longest, 

 the fifth or sixth, at about the middle of K, being one-half or two- 

 thirds the width of the paxillar area. Some of these linear areas are 

 branched once. Oscular orifice large, the bases of the oscular valves 

 being raised above the general level of the paxillar area. The spines 

 of the valves are about 1.5 times the length of the outer spines of the 

 same paxilla; the membrane between the 2 sets of spines with a 

 moderate number of paxillae. 



Adambulacral armature consisting of a single (but on first plate, 2) 

 slender tapering sharp spine (the point of which is frequently 

 broken), normally much longer than the calcareous portion of the 

 aperture papilla, and sometimes exceeding twice its length. A sac- 

 culus is present, but mutilated, owing to injury of the specimens in 

 the net. The aperture papilla is broadly ovate to obovate, usually 

 asymmetrical, and relatively large. Tube feet large, in 2 rows; pur- 

 ple, with a small light-brown sucking disk. 



Armature of mouth plates consisting of 3 or 4 slender, tapering, 

 sharp marginal spines, the series directed across mouth of furrow 

 and spaced from the inner end 'of plate. These spines are very 

 similar to the adambulacral spines and are either subequal or the- 



