265 
central canal, makin-,' with the median ricl.L,re an angle of about 45", or about a right an^rle 
with each other; just beyond these hUeral rid<;es, entirely unconnected with the ridge about 
the central canal, separated from the lateral ridges by a ligament space about the same in 
shape and size as the two lateral ridges, are two more ridges, slightly broader than the 
others; each has a very narrow fan-shaped space beyond it; beyond these two ligament 
spaces, the distal borders of which are approximately at right angles to the dorsoventral 
axis of the joint face, are two large obsolete muscular fossae which are about as high as the 
distance between their proximal border and the dorsal edge of the joint face : these are rounded 
triangular in shape; inwardly each rises somewhat, forming two parallel, very inconspicuous, 
low well rounded ridges, which are interiorly separated by a shallow rounded groove which 
becomes more accentuated just beyond the central canal, where it separates the inner ends of 
the inner pair of ridges; the inner ends of the ligament spa~fces just beyond these ridges are 
bounded by the ridges bordering the muscular fossae interiorly. There is a deep intermuscular 
notch the sides of which make an angle of from 60° to 90° with each other. The ridges on 
the syzygial faces are high, and consequently the ligament fibres are long, appearing in dorsal 
view almost quite as long as those of the neighboring dorsal ligaments. 
All the iiinnules are present; Pj is about 16 mm.; the first segment is slightly trapezoidal, 
viewed from the side about half again as long as broad; the second is between two and one 
half and three times as long as broad, 2.3 mm. long; the following segments are similar, but 
proportionately somewhat longer; the pinnule is moderately stout, like the proximal pinnules 
of the large species of Psatkyromctra, and is somewhat compressed laterally; the first segment 
increases somewhat in diameter distally, the second decreases slightly, and the third also 
decreases slightly, more especially in the ])roximal half; from that point onward the pinnule 
tapers very gradually. P^ is 15 mm. long with ten segments, and resembles Pj ; the fourth 
segment, which is the longest, is about three and one half to four times as long as broad, 
and the fifth is about the same; but the sixth and following are only about twice as long as 
broad, or slightly less. Only the bases of the following pinnules are preserved; thev appear 
to become gradually shorter and more slender, the second segment decreasing rapidly in length 
and progressively decreasing more and more rapidly in diameter distally, on the pinnule of' 
the nintli brachial being not quite so long as its pro.ximal width, and slightly trapezoidal, so 
that the following segments of the pinnule must be very slender. 
In locking into the relationships of this curious comatulid one naturally turns first to 
the family Pentametrocrinidae, in which family the genus Pentametrocrintis also has but 'iw^ 
arms with no I Br .series, and has the first syzygy between the fourth and fifth brachials instead 
of between the third and fourth as usual. 
But in the Pentametrocrinidae (i) the disk is large and stellate and extends far out 
upon the arms, being nearly or quite black in colour; (2) the cirrus sockets are closely 
crowded and irregularly arranged on a rounded conical or hemispherical centrodorsal ; (3) the 
individual cirrus sockets have no fulcral ridges nor produced margins; (4) the radials are 
almost or quite concealed by the centrodorsal; (5) the lower brachials are more or less oblong, 
SIBOGA-EXI'EDITIK XI.Il/'. 34 
