1110 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
Rays very long and rather narrow. Genital inflation extensive though not prominent. The 
genital region extends to about two-fifths or one-half the length of ray. Ray subcylindrical at base, 
very gradually and but slightly widening along the genital inflation; then even more gradually taper- 
ing to the long, very attenuate extremity. Slightly to markedly depressed on basal region; subtrian- 
gular beyond genital region, with a broad median ambulacral ridge, due to the collapsing of this 
abactinal membrane on the ambulacral ridge. Disk large. , Lateral arm-spines long and rigid. Disk 
rather large, subdepressed, but the abactinal surface raised above base of rays, the margin being 
rounded. Abactinal membrane thin, closely beset with delicate, small, sharp, distinctly spaced 
prickles about 0.5 mm. in length. Scattered among the prickles are comparatively few microscopic! 
pedicellarise, together with almost exactly similar but very much larger pedicellarise. The two dis- 
tinct sizes are very characteristic of this species, the larger not being found in the three following 
forms. Interradial plates inconspicuous, with several small tubercles. The abactinal membrane of 
rays is thin and translucent. The inner part of ray is crossed by numerous (35 to 49) transverse, 
annular ridges, rather closely placed, which extend 10 to 20 mm. beyond the limits of gonads. These 
ridges are flexuous and often very irregular. They are placed opposite, or correspond to each adambu- 
lacral plate (beyond the eighth), although occasionally a plate will be skipped. Frequently 2 or more 
neighboring ridges are joined near the radial line, and thence prolonged to the opposite side as a single 
ridge, corresponding to what would ordinarily be the interspace. The ridges are narrow but promi- 
nent, and are composed of many elongated ossicles imbricated end to end, the sutures between which 
are clearly distinguishable when a ray is dried. Along top of ridge are numerous small, spaced, sharp 
prickles. The thin membrane investing the ridge is covered with microscopic pedicellarise. Between 
the annular ridges the abactinal membrane bears illy defined, transverse bands of minute pedicellarise, 
which conform to the course of the adjacent ridges. Among these minute pedicellarise (which do not 
form prominent saccular bands) are numerous much larger pedicellarise, especially abundant on the 
sides of ray. Near base of ray the integument bears numerous scattered prickles of small size. 
Beyond genital region abactinal membrane is thickly sprinkled with pedicellarise, on some rays clus- 
tered into w’ell-defined transverse bands. Only the smaller size is present on the outer attenuate 
portion of the ray. 
Ambulacral furrow fairly wide. Adambulacral plates short (2 mm. in middle of genital region, 
1.25 mm. at base of ray). They are higher than long in basal half of genital region, but gradually 
become lower distad. Each ossicle is slightly concave toward the middle, so that the whole series 
might be roughly likened to the vertebral column of a bony fish. Armature has appearance of being 
crowded, and can be better understood from the figure than from description. At aboral end of each 
plate is a slender, delicate spinelet 2 mm. in length, directed across furrow, reaching and often 
touching its neighbor of opposite side. External to this, on aboral edge of plate, is an oblique trans- 
verse series of 2 or 3 spines, 2 on some plates, 3 on others, these two numbers often but not always 
alternating. When there are 3 spines (4 counting the furrow spinelet) that next to the furrow spinelet 
(near base of ray, at least) is delicate, about equal in length to the former and likewise directed across 
furrow, but farther along the ray it becomes larger and upright. This spinule is absent from those 
plates which have only 2 actinal spines. The next two spines are the same on all the plates. The inner 
is about 4 to 4.5 mm. long, sharp, slender, and upright. The outermost is fully twice as long (9 mm. 
in middle of genital region, even 10 mm. on some arms) and the base occupies the greater part of 
actinal surface of its plate. This spine is sharp, slender, and tapering, and like the others, is invested 
by a thin membrane extending beyond the tip in a short vermiform flap, the whole length of the spine 
being closely beset with minute pedicellarise. The other 2 or 3 actinal spines are crowded at the tips 
and to a les^ extent along their length with the larger pedicellarise also. Near adoral margin of plate 
in a longitudinal line with the innermost actinal spine (the one which is frequently absent) is a deli- 
cate spinelet, shorter than the furrow spinelet, directed upwards or backwards, and like it beset with 
a cluster of the larger pedicellarise. Actinal and lateral faces of adambulacral plates covered with 
scattered pedicellarise of the two sizes, all of them being very deciduous. As is usual in this family, 
the spines are characterized by rather prominent longitudinal ridges or flutings, which are especially 
marked in the largest actinal spines. The series of the latter gradually shortens toward the base of 
the ray, and at fifteenth adambulacral plate they begin to become truncate. From here they rapidly 
shorten, while the tip becomes broader and flaring, and is marked by numerous papillae, while the 
lateral flutings of the stem end in similar peripheral papillae on the crown. These spines are not 
precisely square-tipped, but are cut obliquely so that the summit slopes toward the furrow. 
