356 BULLETIN 76, UNITED STATES NATIONAL MUSEUM. 



adambulacral spines five or four, webbed, the outer standing perpendicular, not 

 subparallel to actinolateral membrane, which is wide; apertures long; aperture 

 papilliB slender, sharp, with slightly convex aboral margin; oral spines five, slender, 

 all ten united by continuous membrane; suboral spine sharp, three-edged, much 

 heavier than oral spines. 



Description. — Abactiual surface very arched and swollen by reason of the rays 

 being more or less drawn together ventrally, and the actinal surface correspondingly 

 concave. Supradorsal membrane rough by the spaced groups of paxillar spines, 

 these groups of five to seven forming a slight or decided protuberance, the mem- 

 brane between the groups being smooth and everywhere punctured by very numer- 

 ous fair-sized spiracles, the whitish sphincters of which clearly define the edges. 

 Pale muscle fibers meander here and there through the translucent membrane, 

 but there are no discoverable muscle bands running between the tips of the spines. 

 It should be added that the spiracles occur also among the spines, but are not more 

 abundant than in the considerable space between the difl'erent groups. In other 

 words, the groups are not crowded together, but are well enough spaced to be 

 counted. Unlike puhnUus, the pedicel of each pseudopaxilla is low, scarcely if 

 any higher than wide, with a crown of five to seven diverging slender spinelets, 

 of which one commonly stands in the center of a circle of four to six; spinelets 

 about 2. .5 mm. long, and the pedicel about 0.75 mm. high. The whole paxilla is 

 thus low, so that the supradorsal membrane is not much raised above the abactinal 

 surface. Paxillie with strong lobes ( four to six) . Membrane with scattered spicules 

 in the form of ci'ooked rods with irregular branches along the sides, these sometimes 

 anastomosing and forming loops. There is no regularity in the form of these rods, 

 which are not crowded as in milifaris. They are never in the form of fenestrated 

 bodies and are more like those of tri.gonodon than militai'ls, though simpler, but 

 yet not so simple as those of ntarsippus. The arcade-like space beneath the supra- 

 dorsal membrane is filled with embryos oriented with either the dorsal or ventral 

 surface uppermost. The specimen is a female. Osculum rather small. 



Ambulacra narrow; feet in two rows. Adambulacral armature consisting of 

 a series of five (distally four) webbed spines curved aborally on the inner end; 

 the inner very short, the next nearh* twice, the third about two and a half, and 

 the fourth about three and a half times length of inner, the fifth subequal to fourth. 

 Membrane deeply emarginate between spines which are not prolonged in a mem- 

 branous sacculus. A peculiarit}- of this species is that the outer spine is not close 

 to the actinolateral membrane, but stands nearly perpendicular, with as much 

 web between it and the membrane as there is between the fourth and fifth spines. 

 Aperture papillae long, slender, and sharp (about one-half length of outer spine), 

 situated about half its length laterally from base of outermost spine. The aper- 

 ture slit is unusually long, extending laterally beyond the edge of the papilla, 

 especially on outer part of ray. The apertures form a conspicuous row of slits 

 along the outer edge of the series of adambulacral fans. 



Mouth plates with five marginal spines graduated fairly evenl}' from the long 

 inner to the very short outer, the whole ten united by a continuous membrane 

 extending to the tips of the spines. The spines are slender and slightly tapering. 



