1112 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
crossed pedicellarise. Interradial plate is conspicuous, confined to lateral 'wall of disk. Abactinal 
membrane of rays thin and translucent. Basal half of each ray crossed by 25 to 32 transverse, 
annular ridges, equidistantly placed, and not nearly so close together as in B. pcmopla. These ridges, 
which begin at the very base of ray, are narrow, prominent, and irregular. They are placed, 
roughly speaking, opposite alternate adambulacral plates, although there are irregularities in this 
respect. Occasionally 2 or more neighboring ridges are joined irregularly in the median radial line 
and variously prolonged to opposite side as a single ridge or as 2 ridges. These annular ridges, as in 
other members of the genus, are composed of slender ossicles, imbricated end to end, which bear 
rather widely separated prickles and microscopic pedicellarise. Membrane between ridges is beset 
with minute prickles, quite numerous at base of ray, but gradually disappearing until they are 
practically absent beyond middle of genital region. Besides these, there are transverse bands of 
microscopic pedicellarise, more or less interrupted on the median radial line. On outer part of ray, 
beyond genital region, the pedicellarise may be scattered, or gathered into more or less definite 
transverse bands. 
Ambulacral furrow fairly wide. Adambulacral plates short and low in genital region (about 2 mm. 
long). They are longer than high, about as broad as long, and are sharply concave -toward the cen- 
ter, as in other species of the genus. Armature recalls that of the preceding species in general features. 
Furrow spinelets are 2, delicate, slender, the aboral situated on the aboral margin of plate, well within 
furrow ; the adoral, very near but not exactly on the adoral edge, slightly more actinad than the aboral 
spinel et. Aboral spinelet measures about 2 mm. in length, but on outer part of ray becomes slightly 
longer. Near base of ray adoral spinelet equals the aboral in length, or is slightly longer (3 mm.), 
but distad is somewhat shorter. Barely a second and shorter spinelet is placed just above the adoral, 
in furrow. All these are sheathed in membrane, which sometimes extends beyond the tip and is 
covered with microscopic pedicellarise. On alternate plates (or less often) the aboral furrow spinelet 
is lacking. Actinal spines 2, in a slightly oblique transverse series along aboral margin of plate in a 
line with the aboral furrow spinelet ( when that is present) . In basal portion of some rays there may 
be 3 actinal adambulacral spines. The inner spine, which is much smaller than outer, measures about 
5 mm. in length in mid-genital region. The outer spine, articulated to a slight boss on plate, is slender 
and needle-like and attains a length of 15 or 16 mm. at outer part of genital region. Both spines are 
invested in membrane, which is prolonged beyond the tip and is closely crowded with microscopic 
pedicellarise. Beyond genital region the adambulacral plates are longer and slenderer. There are 
usually 2 furrow spines, the aboral the longer, and but 1 actinal spine. On plates adjacent to which 
there is a long lateral spine (usually alternate plates), this actinal spine (which represents the outer 
long spine of the basal region of ray) is shorter (about 4-8 mm., according to position) ; but on alter- 
nate plates (between lateral spines) it is very long and slender (9-14 min., according to position). 
Eight or 9 of the outer actinal spines at base of rays are peculiarly modified, as in B. panopla, B. cri- 
cophora, and B. multicostata. These spines are short (4-8 mm. ) and robust, with fluted sides and an 
expanded, truncate, papillose summit, somewhat resembling a composite flower. They decrease in 
length toward the actinostome, the first 1 or 2 spines being usually clavate, acute. In the other direc- 
tion they pass insensibly into the slender pointed variety. Actinal and lateral surfaces of adambu- 
lacral plates are covered with scattered pedicellarise. 
Lateral spines begin at about the eighth or tenth adambulacral plate and are articulated to lower- 
most plate of the annular ridges. These lateral plates are at first free from the adambulaerals, but on 
the outer half of the rays appear to be firmly fused thereto. At base of ray the lateral spines are about 
8 mm. long and gradually increase in length until, in the mid-genital region, they are 15 mm. long. 
This length is kept up to very near the tip of ray, when they abruptly shorten. Lateral spines are 
invested with a membranous sheath extending beyond tip in a short vermiform sacculus and closely 
beset with microscopic pedicellarise. The rays are united at base by first lateral plate of either ray. 
These are rather massive and are articulated also, in the direction the disk, to the interradial plate, 
which forms an elbow projecting outward slightly in the interradial angle at a level with the lateral 
plates. Lateral plates in basal part of genital region few and irregular as to form and arrangement. 
Actinostome not so large in proportion to disk as in the preceding species (about 11 mm.). 
Mouth plates deeply excavated on margin toward furrow (hour-glass shaped). There is the usual 
prolongation, which is not so pronounced as in some species, extending from inner furrow corner of 
plate into the mouth of furrow. Spines numerous. Armature as follows: (1) A short, slender spinelet 
