1030 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
Marginal plates are prominent, forming an angulated margin to ray. Superomarginals, 25 in num- j 
ber from interradial line to the extremity of ray, are confined to the abactinal surface beyond the 
interradial arc, the inferomarginals defining the contour of ray. They are subquadrate in the outer j 
half of arm, but oblong in interbrachial arc, and form a low, slightly arched bevel to abactinal area. 
They are uniformly covered with papilliform granules which are very regular and resemble the cen- 
tral granules of papulae, but are larger. Deep and narrow fasciolar grooves separate the exposed surfaces 
of consecutive plates, the granules covering them being slightly slenderer than the others. 
Inferomarginal plates correspond with the superomarginals, and extend laterally beyond them, 
all this portion being the specialized ridge of the plate. The fasciolar grooves are therefore, as in 
Dipsacaster, very deep and narrow. Outer end of each plate is slightly tumid, the appearance being | 
accentuated by the tufts of spinules. The first 4 to 6 plates bear a transverse series of 3 or 4 short, stout, 
tapering, flattened, sharp spinules. The other plates usually bear 2 such spinules in an oblique series 
on the abactinal end of the plate, but laterally. Considerable variation exists as to the number of 
these spinules. They are sometimes reduced in size and crowded toward the upper end of the plate 
(i. e., on first 4 or 6 plates) and the inner spinule is often spaced from the other 2 or 3. The general 
surface of the inferomarginals is covered with pointed squamiform granules which are enlarged in the 
neighborhood of the spinules to form a small tuft. On the abactinal surface of the plate the granules are 
similar to those of the superomarginals, and in the fasciolar grooves they are slender or spinuliform 
or capillary. 
Adambulacral plates are slightly longer than wide on the rays, shortening near the mouth plates, ? 
Furrow margin convex. Armature as follows: (1) A furrow series of 7, 8, or 9 long, slender, com- | 
pressed, bluntly pointed spinelets, radiating only slightly. The tips form a convex edge to the comb. j 
The lateral spinelets are often conspicuously shorter than the others. (2) On the ray the actinal sur- 
face of each plate bears 8 or 9 shorter tapering spinelets, disposed usually in 2 semicircular rows, those I 
of the series nearest furrow series the longer. There are besides 3 to 5 still smaller spinelets along 
both adoral and aboral edge of plate, extending over the grooves which separate the plates. These 
grooves are continuous with those passing between the actinal intermediate plates, which in turn 
communicate with the much deeper furrows between the exposed surfaces of marginals. The spinelets 
are not webbed, however. The first 3 or 4 adambulacrals possess fewer furrow spinelets (6 or 7) I. 
because the plate is shorter. The actinal spines are less crowded (15 to 23) and are arranged in a 
rather definite series along both adoral and aboral margins, with 2 intermediate transverse or obliquely j 
transverse series. The first longitudinal actinal series is sometimes well defined on the plates. Many 
variations in arrangement occur. 
Mouth plates are prominent actinally, fairly large, the exposed surface curving strongly dorsad 
toward the mouth. Armature consists of a furrow series of 8 tapering, long, slender spinelets, bluntly 
pointed and increasing in length toward the inner angle. The inner spinelets are slightly flattened 
and are usually turned away from the mouth, but the outer members of the series extend about half- 
way to the outer end of plate, to which the series is continued along the margin adjacent to first adam- 
bulacral as a row of much smaller, slenderer, spinelets (8 to 10 in number). Actinal or exposed sur- 
face bears a series of slender, tapering, bluntly pointed spinelets along margin of suture. On the 
mouth angle these are about as long as adjacent marginals, but rapidly decrease in length as they 
proceed outward, becoming short and round-tipped. On outer half of each plate an intermediate, 
subparallel, and similar series is present, often, however, arranged irregularly, so as to give the appear- 
ance of 2 intermediate series. Spinelets of mouth angle usually appear crowded or bunched together. 
Actinal interradial areas fairly large, paved with close-set roundish plates, which extend nearly 
halfway to tip of ray (to ninth inferomarginal plate). These plates are arranged in series extending 
from inferomarginals to adambulacrals, and those plates adjacent to the latter are larger than the 
others. When viewed from the surface toward body cavity, the plates are seen to be imbricated, the 
outer end of each being slightly elongated and overlying the inner rounded end of the adjacent plate. 
Regarded from the actinal surface, it is the inner end which overlies the outer. On the rays this inner 
end is somewhat elongated, and the series adjacent to the adambulacrals slightly overlaps the outer 
margin of the latter. Central portion of each plate is raised into a regular paxillar tabulum with a 
convex summit, surmounted by a radiating central group of 6 to 10 short, rounded, subconical, pointed 
or blunt-tipped, granuliform spinelets, with a peripheral series of about the same number of slender, 
slightly longer spinelets placed at a lower level on the pedicel or tabulum. Often the central and 
