1016 
BULLETIN OF THE UNITED STATES EISH COMMISSION. 
irregular as to length and position, scattered along the aboral margin below the inner marginal series. j 
They are wholly covered by the much larger spines of the first series. General surface of plate is j 
covered with papilliform spinelets, crowded, becoming slenderer in the deep fasciolar grooves. 
Adambulacral plates, wider than long, have a convex margin to furrow. Armature as follows: 
(1) A furrow series of 3, with which are associated the lateral spines of the first actinal series, making 
usually 4 or 5 spines on the margin. The median spine is stoutest, most flattened, the 2 laterals 
decreasing in length and forming a palmate series. The furrow spines proper are truncate or round- 
tipped, tapering and compressed, the edge being toward furrow. The median spine reaches quite 
across the furrow. (2) Actinal surface bears 3 or 4 longitudinal series of tapering spines, decreasing 
in length toward the outer end of plate. The first, or inner, 2 series have about 3 spines each, while j 
the outer 2 commonly have 4, although there is much irregularity. The spines of the inner 2 series | 
are longest, and are slightly flattened, the broad side to furrow. 
Opposite each adambulacral plate is a roundish intermediate plate, with a central raised tabulum, - 
the series of which extends to the 55th inferomarginal or to within 12 mm. of the tip of ray (pi. I 
in, fig. 1.) Actinal interradial areas fairly large, considering the small size of disk, and paved with .' 
round plates like those of the rays. There are about 16 of these plates, omitting the series adjacent to 
the adambulacrals, and they do not extend beyond the second inferomarginal. Intermediate plates of 
ray are armed with a radiating group of 15 to 18 blunt spinelets, resembling the papilliform spinelets ■ 
of inferomarginals but larger. Rarely a central spinelet is enlarged. In interradial areas each plate 
bears a conspicuous, bluntly pointed, tapering spinule, about which are grouped 2 to 5 shorter spinelets. 
Surrounding these is a peripheral series of numerous, still shorter, papilliform, slender spinelets, j 
radiating to form a rosette, the whole armature surmounting the central tabulum of the plate and j 
forming a very ornamental paxilla-crown. On those intermediate plates adjacent to adambulacrals 
the armature is the same as on ray, except for the presence of 1 or 2 larger central spinelets. 
Mouth plates are rather prominent, bent inward toward actinostome. At the inner angle there 
are 4 heavy, slightly flattened, blunt spines, placed in a perpendicular comb, the largest nearest 
mouth, and the series of companion plates are close together, forming a double phalanx at each mouth 
angle. This series is continued toward outer angle of plate as a row of stout, slightly flattened, blunt 
spinules, along the margin of suture. They are all much smaller than the inner teeth, and become . 
slenderer and weaker as they approach the outer end of plate. Marginal spinelets small, flattened, 
rounded or truncate at tips, extending in a perpendicular series along border, subparallel to the 4 
“teeth,” and appressed to an intermediate row of spinelets. Between marginal and superficial series 
are 3 parallel intermediate series, the one nearest teeth slightly larger than marginal spinelets. These 
3 intermediate series are continued toward the outer end of plate as slender and longer spinules form- 
ing a bristling armature to actinal surface. A deep fasciolar groove intervenes between the mouth 
plates and adjacent adambulacral, and that surface of the former which forms the side wall of groove 
is covered with minute papilliform spinelets. Superambulacral plates well developed. 
Madreporic body small, situated slightly nearer margin than midway between it and the center 
of disk. Ridges are rather coarse, having alternate swellings and constrictions, and cross the plate 
interradiallv in direction. 
Color in life unknown; in alcohol dull brown. 
Locality: Station 3935, vicinity of Laysan Island, 57 fathoms, white sand, broken shells, coralline; 
bottom temperature 71.1°. Type no. 21147, U. S. National Museum. 
This species may be distinguished by its long rays and generally flattened form, by the unarmed 
superomarginal plates confined almost entirely to the abactinal surface; by the broad, band-like infero. 
marginals with their numerous small spines; and especially by the series of intermediate plates between 
the adambulacrals and inferomarginals. The species has the general facies of a flat, long-rayed \ 
Astropecten, with acutely angular yet rounded margin to rays. It is sufficiently unlike Astropecten, in 
the presence of a series of actinal intermediate plates on the ray and in the character of inferomarginal 
armature, to warrant its segregation from that much overburdened genus. 
