1020 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
I 
Abactinal paxillar area is rather uniform in character, but not very compact, except in center of I 
disk, the paxillse being spaced so that the papulae may be detected between them. The latter are 
crowded into rows between the regular transverse lines of paxillse. Along a very narrow median line j 
on each ray, where paxillse are not regularly placed, the papulae are wanting, and they appear to be I 
absent also from center of disk. Paxillse are rather small and decrease slightly in size toward median j 
radial line, extremity of ray, and center of disk. Each paxilla consists of 2, 3, or 4 central papilliform j 
spinelets surrounded by a peripheral series of 7 to 10 similar spinelets. The latter may radiate like - 
the petals of a flower, or the whole form a coordinate group. The more numerous paxillae possess 
about 2 central spinelets and 7 to 9 marginal ones, while the largest may have upward to a dozen mar- ; 
ginal spinelets. In specimens from off the south coast of Oahu, which differ slightly from the type, ! 
the paxillse are usually more crowded and the spinelets form a coordinate group, giving the abactinal 
surface a much more compact appearance. In proportion to size of animal the paxillse of these speci- ; 
mens are a trifle larger than the type, but the number of spinelets does not appear to average greater. \ 
Superomarginal plates, 57 in number from the interradial line to extremity of ray (or 60 in largest j 
specimens, with R=120 mm.), form a somewhat rounded bevel to margin of ray. Plates short and 
high (or wide), the longest being the tenth to fifteenth from the interradial line. Each plate has a 
specialized ridge, the ridges of consecutive plates being separated by rather narrow transverse fasciolar ! 
grooves, for the most part obscured by crowded papilliform spinelets. It is the exposed, very slightly j 
tumid face of these ridges which forms the outer or exposed face of the plates on the dorso-lateral 
face of the ray. The plates are covered with crowded, short, papilliform spinelets, each of which is 
invested with a membranous sheath. On the outer two-thirds of the ray (beyond the eleventh or j 
twelfth superomarginal) each plate has 1, 2, or sometimes 3, short, delicate spinules placed in a median ' 
transverse row at about the middle of the plate. The spinelets surrounding these are flattened or j 
squamiform. The spinelets lining the sides of the fasciolar grooves are very much slenderer than J 
those of the exposed surface of the plates, the latter being much more crowded about the edges than !i 
in the center. 
Inferomarginal plates correspond exactly to the superomarginals, and form an abruptly rounded j 
margin to actinal area. When the ray is viewed from side the whole height of supero and infero-mar- 
ginal plates can be seen. Inferomarginals are considerably higher (or wider) than long, and like the 
superomarginals possess an especially elevated ridge, the successive ridges (the exposed surface of the 
plates) being separated by fasciolar grooves filled with papilliform spinelets. Plates are covered with . j 
crowded spinelets, similar to those investing the superomarginals, which increase slightly in size } ! 
toward the actinal intermediate plates. Each plate carries a row of 3 flattened, tapering, sharp spines, j 
directed obliquely upward and toward end of ray. These are placed in a median dorso-ventral line, 
the middle spine being longest (in length equaling 2 inferomarginal plates, or their exposed surfaces) . 
All 3 are closely appressed to the ray. On outer third of ray there are only 2, the upper spine’ ’ 
being absent. On the proximal 2 or 3 inferomarginals there are usually only 1 or 2 spines, reduced in 
size. A few of the largest specimens possess a series of 4 spines on the more proximal inferomarginals, 
but the number is usually 3. In the specimens from the south coast of Oahu, already alluded to, the 
spinelets covering both supero and infero-marginals are more thickly covered with membrane, appear 
more fleshy, and tend to be more squamiform. Those of the inferomarginal plates are particularly * 
soft. They increase in size actinally, on the lower part of the plate being rather larger than the 
papillae of adjacent actinal intermediate plates. 
Adambulacral plates massive, about as wide as long, with an angular margin to furrow- The 
plates are separated by fairly conspicuous sutures, forming shallow grooves usually continuous with 
the fasciolar grooves between the marginal plates. Adambulacral armature as follows: (1) A furrow 
series of 7 or 8, occasionally 9, rather long, flattened, blunt spinelets, the central ones being very 
slightly the shortest. These spinelets are so arranged that about 4 are placed along either side of the 
angular margin. The median 2 or 3 spinelets are compressed so that the edge is toward the furrow, 
but the lateral ones present their flattened face thereto. Considerable of the flattening, which is 
more pronounced at the base of the spinelets, is due to the membranous envelope of each. (2) The 
remaining spinelets, more or less grouped and 10 to 15 in number, form a rather compact group on the 
actinal surface. They are tapering, blunt, and are usually disposed in 3 irregular longitudinal rows. 
These actinal spinelets are often thicker than the marginal series, and are invested with a rather pulpy 
membranous sheath, which frequently flattens in the outer spinelets of plate (especially in specimens 
