THE STARFISHES OF THE HAWAIIAN ISLANDS. 
1101 
Genus BENTHASTER Sladen. 
Benthaster Sladen, Journ. Linn. Soe. London (Zool.), vol. xvi, 1882, p.'242. Type Benthaster wyville-thomsoni Sladen. 
Benthaster eritimus, new species. 
PL xxxviix, fig. 7; pi. XL, figs. 1, la-b. 
Marginal contour substellate, interbrachial arcs wide, angular, and only moderately indented. 
R=10.5 mm.; r=6 mm. 11=1.75 r. Rays taper gradually from a broad base, tips upturned. 
Abactinal surface slightly convex, rather depressed. Actinal surface slightly convex. 
Supradorsal membrane is very delicate, transparent, appearing scarcely more than a film. It is, 
however, remarkably resistant, and when examined under the microscope by transmitted, or even 
reflected light, small muscle fibers can be distinguished meandering through the membrane, forming 
an illy defined net work. There are, besides, small spiracula (?) scattered here and there. Each 
appears to be surrounded by a thickening of the membrane, making the aperture well defined when 
the membrane is examined by transmitted light. But on account of the small size of the animal, these 
spiracula are quite microscopic, and are impossible to distinguish except in a strong light. It is barely 
possible that they are apertures through which the spines of the paxillse protrude (the spines having 
been broken), but this is in no wise probable from their numbers and position. There is not more 
than 1 to an indefinite mesh of the muscular reticulum, but they do not occur in all the meshes. The 
membrane can scarcely be called spongiform, the term used by Sladen in describing B. wyville-thomsoni 
and B. penicillatus, for it is thin and of uniform thickness throughout. Paxillse are fairly numerous 
and are well spaced. Pedicels are long (for genus), slender, and delicate, springing from delicate 
cruciform plates with long processes. Pedicels on disk (1.75 mm. long) are about one-hall the length 
of spinelets. The latter are relatively long, delicate, glassy, about 8 to 10 to each paxiJla of disk, and 
about 5 on outer part of ray. They are swollen slightly at base for articulation to tip of pedicel, radiate 
slightly apart, and protrude for the greater part of their length beyond the supradorsal membrane. 
Each spinelet appears to be perforated along its entire length by minute holes, and to be made up of 3 
rods coalesced, so that a cross-section would appear trilobate. 
Cruciform plates, from which the pedicels spring, have remarkably long, slender processes, which 
are usually unequal. There is no tendency for them to become rotund or squamiform. Oscular orifice 
is large. The “valves” are large, radial in position, the pedicel much enlarged, and expanded at 
the top as in Hymenaster. A muscle band joins the crests of the pedicels as a sort of sphincter. Spine- 
lets many, arranged on the expanded top of the valve pedicel in about 3 series. Papulae are large, 
full, bilobate or trilobate, pulpy sacs, constricted at the base, few in number, and are situated on 
either side of the ray near the base. Just external to one of the valve ossicles is the small, incon- 
spicuous, madreporic body. Anal opening prominent. 
The “ supermarginal” plates are reduced to 2, which form anarch over the terminal tentacle 
and are armed with a tuft of numerous spinelets. They appear to be smaller, or at least to extend 
not so far orad as in the other 2 species. 
Adambulacral furrows are wide. Tube feet large, in 2 series. Armature of adambulacral plates 
consists of a series of 5, long, slender spinelets, which are invested by an exceedingly delicate mem- 
brane. They are placed along the furrow margin, often somewhat obliquely on account of the 
obliquity of the plate itself. The longest spinelets reach across the furrow. They decrease in length 
toward the aboral end of the series, the outermost being much shorter than the other 4, which are 
not greatly different in length. Segmental apertures are apparently absent, but a flattened, short, 
lanceolate-acuminate spinelet, devoid of any perceptible membrane, stands on the actinal surface of 
the plate, and is bent outward over the actinolateral membrane.’ This spinelet is enlarged on the first 
adambulacral plate, is flat, thin, and irregularly multifid. It is lodged in the actinolateral membrane 
just external to the mouth plates, and seems to serve as a support for the membrane. 
The mouth plates are of the Hymenaster type. They are prominent actinally and aborally. 
Armature ,as follows: (1)2 slender spinelets on actinal surface of plate near median suture, the outer 
slightly farther from the suture than the inner. (2) On the margin near the suture, 2 slender spine- 
lets, the outer of which is about one-half the length of the inner, which stands in a linear series with, 
and is exactly similar to the innermost actinal spinelet. Two much smaller spinelets stand on a 
slight lateral flange of the plate and are usually directed into the mouth of the ambulacral furrow. 
All the spinelets are tapering and sharp, and the larger, at least, are encased in a delicate membrane 
which is only evident at the tip. 
