158 
JR. Rathbun — List of the Brazilian JEchinoderms. 
there traces of their points of attachment. Around the edge of the 
piece is a single row of twelve to sixteen cirri, each composed of 
eleven to twelve simple joints, in addition to the large, incurved, 
sharply-pointed terminal spine. First joint very short ; second as 
long as broad ; third to sixth or seventh longer than broad, some- 
what constricted toward the centre, or enlarged at the ends, so as to 
produce a series of swellings along this part of each cirrus ; the 
remaining joints, to the tip, decrease successively in size, and are 
slightly compressed laterally, the last three bearing each a minute, 
sharp tubercle at or near the upper distal end. 
First radial slightly exposed ; axials low, pentagonal ; usually 
three brachials between first and second axials, and one brachial be- 
tween second and third axials, when the latter occurs. At base of arm 
the joints are simple; but shortly after the last division they become 
rather long, and well-separated, with an oblique distal edge, which 
is thin and slightly raised so as to appear imbricating ; this edge ter- 
minates in a row of minute, sharp tubercles. The first pinnule starts 
from the second joint after the first division ; after the second divi- 
sion, there is a pinnule to each joint on alternate sides, with seldom 
an intervening joint. The first pinnules are very long and slender, 
their length being equal to about the diameter of the oral surface of 
the disk, or slightly longer. They are composed of rather elongated 
joints, those toward the base having their distal ends, on two sides, 
thin, slightly elevated and minutely spinose. The last seven to ten 
— not including the three terminal ones — bear each a very large, 
irregular tubercle, which is nearly as long as the joint itself. In 
alcoholic specimens these pinnules curve gracefully over and lie 
entangled together upon the oral side of the disk, appearing not 
unlike the young, unfolding fronds of a fern. The second pinnules 
are similar in structure to the first, but shorter. The others, to tlie tips 
of the arms, are of subequal size throughout, and from one-third to 
one-half the length of the first; they are rather broader at the base, 
and each of the three terminal joints composing them is marked with 
a minute, sharp tubercle. 
Oral surface very minutely granulose ; mouth eccentric ; anus 
nearly central, raised on an elevated, conical promineuce. 
