1008 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
arranged in 3 distinct series of 3 each, the spinelets of the 2 actinal series being flat, rather short, with 
expanded, roundly truncate tips; armature of mouth plates; size of actinal interradial areas, and num- 
ber of actinal intermediate plates, these being less numerous in pectinatus. The present species may 
be readily distinguished from other known Hawaiian forms by the presence of an oblique comb of 3 
or 4 comparatively short, appressed, close-set spines on the sides of the inferomarginal plates, and by 
the presence of a small, erect spinule on all the superomarginals. 
Astropecten pusillulus, new species. 
PI. i, fig. 3; pi. II, figs. 4, 4a-b. 
Rays 5. R=33 mm.; r=6.5 mm. R=5r. Breadth of ray at base (between first and second 
superomarginals) 6.5 mm. 
Rays long, slender, delicate, flexible; tapering from -a narrow base to a blunt point. In many 
specimens the outer half of ray has the sides subparallel, then abruptly tapering at the extremity. 
Disk small; general form depressed, but abactinal paxillar area inflated both on disk and rays. A 
slight epiproctal elevation usually present. Actinal surface slightly convex. Interbrachial arcs 
subacute. 
Abactinal integument rather thin and the paxillar area uniform and compact. Paxillse not 
arranged in definite order. Each arm is marked off from the disk by a shallow furrow in the inter- 
radius, which broadens toward the center of the disk', and insensibly grades into its fellows of the 2 
neighboring interradii. In this way a stellate area is often formed in center of disk, due to the greater 
inflation of radial areas, and characterized by a much more compact arrangement of paxillse. Paxillse 
decrease in size toward median radial line, extremity of ray, and center of disk, the largest being 
found, therefore, in the interradii, and the lateral portions of the base of rays. Each paxilla consists 
of a columnar ossicle, flaring at the base, surmounted by a single central spinelet which is surrounded 
by a peripheral row of 6 to 8 club-shaped, papilliform spinelets, each invested with a rather thick 
layer of membrane. These spinelets are a trifle longer than the basal portion of the paxilla, and 
they do not usually radiate a great deal. Smaller paxillse on the arms have 4, 5, or 6 spinelets in the 
marginal series, and lack the central spinelet. The calcareous portion of these spinelets is slender and 
cylindrical, the membranous investment producing the clavate appearance. 
Superomarginal plates, 31 in number from interradial line to extremity of ray, are about as broad 
as long, except on the outer third of ray, where their length exceeds the breadth. First 3 plates are 
higher than long. They form a conspicuous, slightly rounded bevel to margin of paxillar area, tend- 
ing to become flattened on the outer half of ray, but almost perpendicular in the interbrachial arcs. 
For a considerable portion of the outer two-thirds of ray they are nearly uniform in size. All are 
uniformly covered with papilliform granules or spinelets, much larger than those of paxillse, clavate 
or sometimes slightly squamiform in shape, each spinelet invested with a pulpy sheath. No spines on 
superomarginals. Furrows between plates deep, forming well-developed fasciolar grooves. 
Inferomarginals correspond in number to superomarginals, and are placed exactly opposite to 
them. They are much wider than long, forming an even, rounded bevel to sides of actinal surface. 
They extend but slightly beyond superior series, are armed with an oblique row of 2, or in largest 
specimens, 3, short, stout, tapering, sharp-pointed spines, placed near the upper or lateral margin. On 
the outer half of ray the series is rather nearer the aboral than the adoral margin. When there are 
3 spines, the 2 outer, or upper, are of about equal length, and considerably longer than the lowest; 
when only 2 are present, the third to sixth inferomarginals usually have an extra spinule added to the 
inner end of the series. On first inferomarginal plate, the spines are more reduced in size, and 2 
extra spines are added, while 1 is added to the series on the second and third plates. General surface 
of plates covered with papilliform “barley-corn” spinelets, similar to but- larger than those covering 
superomarginals. 
Adambulacral plates with convex margin to furrow. Armature is arranged in 3 series on inner 
part of ray, but becomes reduced to 2 on the outer half. Inner or furrow series consists of 3 spinelets 
which are rather short, the middle one larger than the laterals, and slightly tapering, being flattened 
to produce a blunt-ended blade with the edge toward furrow. The 2 lateral spinelets are slender and 
tapering. The 2 spinelets of the second series are associated with the furrow series on the proximal 
plates in large specimens. Second and third (actinal) series consist of 2 tapering and pointed spinelets 
