THE STARFISHES OF THE HAWAIIAN ISLANDS. 
1037 
Pseudar chaster myobrachius, new species. 
-PI. x, figs. 6, 6a; pi. xix, 1, la-c. 
Rays 5. R = 34 mm. ; r = 13 mm. R = 2.61r. Breadth of ray at base, between second and third 
snperomarginal, 12 mm. ; halfway to tip, 7 mm. 
Rays rather narrow and short, slightly tapering after the basal expansion to a pointed extremity. 
Interbrachial arcs wide and well rounded, so that base of rays is broad. Margin of rays evenly 
rounded, more beveled on disk. 
Abactinal paxillar area compact and uniform; very narrow on rays, consisting of only three rows 
of plates on outer half, where it is less than half as wide as a superomarginal. Paxillse roundish to 
subpolygonal, close-set, and not arranged with any great regularity. The pedicel is surmounted by 
12 to 18 coordinated, short, truncate, 3- or 4-sided spinelets, prismatic in appearance. A few of the 
peripheral spinelets are usually noticeably smaller than others. Paxillse decrease in size toward 
margin and on rays, where there is usually only 1 central spinelet with 7 to 9 surrounding it. A well- 
defined groove is present between the paxillar area and marginal plates. Papulae absent from distal 
half of ray. 
Superomarginal plates, 23 in number from median interradial line to extremity of ray, form a 
broad, conspicuous margin to abactinal area. Length in interbrachial arc less than on ray (except 
outer fourth). Plates are covered with a close polygonal granulation, the granules increasing in size 
and becoming less crowded toward outer end of plate. A marginal series of much smaller granules 
surrounding each plate is clearly distinguishable. Plates of outer half of arm have an oval naked spot 
on middle of dorsal aspect. This area begins on ninth or tenth superomarginal and is present on 9 or 
10 plates. The last (distal) few plates, being very small, are completely covered with granules. 
Inferomarginal plates correspond in number to superomarginals, and encroach rather more upon 
actinal area than do the latter upon abactinal. Plates in interbrachial arc are conspicuously shorter 
than those on ray. They are covered with numerous granules, which increase conspicuously in size 
toward outer margin of plate. Most of the granules are flat-topped, roundish, or polygonal, but many 
show a tendency to become squamiform. Plates of interbrachial arc bear a median transverse series 
of 4 flattened, tapering, sharp spinelets which have a swollen base and are closely appressed to the 
plate. These are reduced in number to 3 and 2 on ray, and finally to one on outer part. The series is 
well spaced. 
Adambulacral plates have an angular furrow margin, the apex of which is nearer adoral than 
aboral side. The armature consists of a furrow series of 6 or 7 short, roundly truncate, flattened 
spinelets, 4 of which are on that side of the angular margin turned away from mouth, the longest 
spinelet at apex, and the other 2 on the adoral side of the margin. They thus form a palmate series 
and are graduated in length. Furrow series is continued along adoral margin in 2 to 5 gradually 
shortening spinelets, and similarly along the aboral margin in 2 or 3 spinelets. In middle of actinal 
surface there is an erect tapering spinule, more prominent than any others of plate, and clustered 
around it are numerous small, papilliform spinelets, especially toward the outer side of plate. On 
first few plates the prominent spinule is not present. The spinelets which are found along the adoral 
and aboral margins of each plate are opposed over a sort of fasciolar furrow between the plates. 
Actinal intermediate plates are subquadrate or roundish, large, and do not extend beyond the 
third inferomarginal. They are arranged in about 3 series parallel to the adambulacrals, and increase 
in size toward disk. They are covered with round papilliform granules, which are truncate, well 
spaced, and often arranged in more or less definite rows. No fasciolar grooves are present between 
the plates, or if present can not be regarded as in any manner specialized. 
Mouth plates are large, ovoid, and prominent actinally, with an extensive furrow margin. The 
armature consists of a furrow series of 7 blunt flattened spinelets, similar to but larger than the adam- 
bulacral furrow spinelets, increasing in length toward inner end of plate. These inner spinelets are 
slightly compressed in an interradial plane, and likewise taper a trifle. A superficial series of 10 is 
present along the margin of the median suture, decreasing in length toward the outer end of plate, the 
outermost being scarcely more than flat-topped granules. Furrow series is continued along margin 
adjacent to first adambulacrals in about 6 short, graduated, very flat spinelets, opposed to those of the 
adjacent edge of adambulacral. Between these and superficial series is a row of 3 or 4 small papilliform 
granules, similar to the adjacent superficial series. 
