THE STARFISHES OF THE HAWAIIAN ISLANDS. 
1019 
6. in all. (2) Actinal spinelets of plate, 15 to 30 in number, decrease in length from the furrow toward 
the marginal plates. There are 3 fairly regular longitudinal series in the inner half of plate. At base 
of ray the first series has 3 or 4 spinelets, the second 3 to 5, and the third about 4 or 5. On outer por- 
tion of ray the spinelets are rather more numerous. Besides these, on the outer half of plate is a 
variable number of smaller spinelets, not regularly arranged. Many plates have 5 or 6 spinelets, usu- 
ally on the aboral side, arranged in a definite, conical, pedicellarian apparatus. 
Actinal interradial areas are small, paved with small, roundish plates, the series of which, in a 
rudimentary condition, extend about two-thirds the length of ray (to twelfth or fifteenth inferomar- 
ginal). In interradial areas the plates are arranged in series extending from inferomarginals to adam- 
bulacrals, and the number of series, with the number of plates in each, is as follows: First inferomar- 
ginal, 3 series, 5, 4, and 3 plates, respectively; second inferomarginal, 2 series of 2 plates; third 
inferomarginal, 2 plates adjoining sixth and seventh adambulacrals. Beyond this point intermediate 
plates become rudimentary, 1 or 2 being fastened to the lower border of each inferomarginal. Arrna- 
ture consists of long, delicate, slender spinelets disposed in a group similar in all respects to those of 
adjacent portions of adambulacrals. Spinelets on those plates nearest interbrachial arc are shorter, 
resembling more nearly the spinelets of adjoining inferomarginals. 
Mouth plates are elongate, the united pair ovoid, prominent, broadest toward actinostome-. 
Armature conspicuous and irregular, as follows: (1) A marginal series of about 6 short, blunt, usually 
somewhat flattened spinelets, which, with those of the companion plate, form a compact, crowded, 
fan-shaped group at each mouth angle, the angular space between the meeting series being filled with 
similar spinelets. (2) On actinal surface a superficial series bordering the suture, stout, short, flat- 
tened, with rounded, truncate or flaring, leaf-like tips, and narrowing at base; this sort confined to 
the inner half or two-thirds of plate, the outer portion of series being composed of slenderer, flattened, 
sharp spinelets. Innermost 2 or 3 spinelets of superficial series are often enlarged to form teeth (a, 
fig. 1 e, pi. ix), which are flattened, oblanceolate, blunt, or truncate. The edge of the plate toward 
actinostome is angular, like the adambulacral plates, so that the marginal series of 6 or 7 spinelets 
( b , fig. 1 e, pi. ix ) is also angulated, and is continued along the border adjacent to the first adambu- 
lacral as a series of weaker and smaller spinelets. Between this and the superficial series are 2 more 
or less irregular rows of similar but larger spinelets placed parallel to the former and increasing in 
length toward the inner end of plate. 
Madreporic body is fairly large, situated about its own diameter distant from margin; striations of 
medium coarseness, radiating from an eccentric point. 
Color in alcohol bleached yellowish to whitish; in life, unknown. 
Localities: Type (no. 21148, U. S. National Museum) from station 3918, 8 miles southwest of 
Honolulu, 294-257 fathoms, white sand and mud; bottom temperature 44.5°. Taken also in this 
vicinity at station 3914, 289-292 fathoms, gray sand, mud; and at station 3919, 257-220 fathoms, gray 
sand; 16 specimens taken in this cruise. Cruise of 1891: Station 3473, south coast of Oahu Island, 313 
fathoms, fine gray sand; 1 specimen. 
This peculiar species was taken only in a very limited area off the south coast of Oahu Island. It 
is readily distinguishable by its delicate paxillar area, small superoinarginal plates, and especially by 
the remarkably tumid inferomarginals with their armature of long, exceedingly delicate, slightly 
curved spines. 
The stomach contents of several specimens included small gastropods, pteropods, ophiurans, young 
sea-urchins, ostracod and macruran crustaceans, and small worms in tubes. 
Genus PSILASTER Sladen. 
Psilaster Sladen in Narr. Challenger Exp., vol. v, 1885, p. 611. Type, Astropecten andromeda Muller and Troschel. 
Psilaster attenuatus, new species. 
PI. Ill, fig. 3, 3 a-d; pi. VII, fig. 4; pi. VIII, fig. 1. 
Rays 5. R=107 mm.; r=17.5 mm. R=6 r. Breadth of ray at base (between second and third 
superomarginal plates) 18.5 mm. 
Rays elongate for genus, rather narrow, with a relatively narrow base, thence gently tapering to 
a slender sharp extremity. Interbrachial arcs acute, but sharply rounded. Disk relatively small. 
Abactinal area plane; actinal area plane; disk capable of slight inflation. 
