1068 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
lines of most of the plates in the living and alcoholic specimens. When dried, the membrane shrinks 
very much, and on the dorsal surface reveals a sparse and very minute granulation. Granules of 
marginal and actinal plates are coarse and conspicuous in the dried state, but are not very conspicuous 
in the living or alcoholic specimens on account of the pulpy consistency of the skin. 
Abactinal surface is subplane to slightly convex, covered with a wrinkled, rather thick membrane 
which reveals the plates beneath when dried. In each median interradial line there is a sharp crease 
extending inward toward center of disk, while similar lines extend toward center of radial area from 
each suture between superomarginals. Everywhere the skin is traversed by fine creases. Radial areas 
are conspicuous by the black papulae which have passage at corners of hexagonal plates, and thus 
indistinctly mark out their form. Papulae wanting on median interradial region. Plates are further 
revealed in fresh specimen by creases which radiate from papular pores. The fine granulation is not 
apparent in the undried state. Pedicellariae wanting on dorsal surface. If the skin is stripped off 
(which is done with difficulty), the arrangement of plates is then easily seen; or the specimen may be 
dried. Plates are polygonal and rather irregular. A fairly regular series extends along median radial 
line, the remainder being arranged parallel to this. Median series does not reach tip of ray, the outer 
6 or 7 superomarginals of either side being in contact medially. The other series do not extend so far 
as the median, but end one after another in conformity with the taper of the ray. External to median 
radial series on each side is an irregular series of much smaller plates which extend but a very short 
distance beyond the base of the ray, where they die out gradually. The plates of next series external 
to this are large as the median radial, and are adjacent to them after the disappearance of the smaller 
intermediate series. The third longitudinal series consists of even smaller and more irregular plates 
than the first or intermediate series. (This series is not apparent in largest specimens, and when 
present it does not extend so far distad as the other intermediate plates. ) Fourth series as large as 
second. Opposite the fourth superomarginal one can count 6 or 7 longitudinal rows at either side of 
the median radial series.' Occasionally the smaller intermediate plates form a partial series around 
the larger plates, but in this case they are smaller than the longitudinal series of intermediates. No 
definite arrangement over center of disk, which is paved with rounded or subpolygonal, large and 
small plates mixed together. Interradial plates are regular in type — hexagonal to quadrate — but may 
be irregular in smaller specimens. If abactinal area is treated with caustic potash and viewed from 
the internal (or coelomic) side, some of the smaller intermediate plates (hot those of the longitudinal 
intermediate series, but still smaller plates) are seen to form short, connecting, radiating ossicles 
between larger plates of the median radial area at base of ray nearly to center of disk. Their 
arrangement is irregular, however, and some of the smaller plates of the disk are rudely substellate. 
This point is, however, not at all evident when the plate is viewed from the dorsal side. The 
so-called connecting ossicles appear merely as irregular small plates between the larger polygonal 
ones. In large specimens these smallest intermediate plates are scarce; and they are by no means 
constant in number or position in the medium-sized and small specimens. But the presence of an 
intermediate incomplete series of secondary plates at either side of the median radial series is constant. 
Marginal plates are well developed. Superomarginals, 20 in number from median interradial 
line to extremity of ray, are wider than long, and form an arched border to body. In a few smaller 
specimens the inferomarginals extend laterally slightly beyond superior series on disk. In this case 
the superomarginals form more of an arched bevel. They are covered with tough membrane, in 
which are embedded 8 to 20 subspherical granules spaced over the central portion of plate. These 
are absent from outer half of ray. The first superomarginal is slightly shorter than succeeding 4 or 5. 
Inferomarginals correspond in number to superomarginals, but are not always exactly Opposite 
to them at base of rays. They are much broader than high, and encroach conspicuously upon actinal 
area, being covered with numerous scattered granules imbedded in membrane. These increase in 
size toward outer edge of plate, and are largest on the lateral face of ray, where they are as large or 
slightly larger than the granules of superomarginals and decidedly more numerous and close-set. 
Terminal plate prominent, pentagonal, armed with 3 terminal, thimble-shaped granules. 
Adambulacral plates longer than wide, with a faintly convex furrow margin. Armature consists 
of 7 (occasionally varying to 6 or 8) short, blunt, slightly compressed spinelets, which form a radiat- 
ing palmate series and are covered with membrane, which as a sort of web, unites them for a short 
distance above the base. Usually the end spinelets are much shorter than the median, the whole 
forming a rattter regular graduated series. Actinal surface of plate, like remainder of body, is covered 
