REPORT ON THE CRINOIDEA. 305 
himself under the name of Pentacrinus decorus. He was thus led to state that while the 
two outer radials of Pentacrinus asterius are united by syzygy, those of Pentacrinus 
miilleri are articulated, a mistake almost the opposite of that made by Liitken. It is not 
difficult to understand how Miiller’s error arose ; for the line of syzygy is not dotted as it 
is in the Comatul, where the apposed faces are marked by radiating ridges. There is 
little or nothing of this striation on the syzygial surface of Pentacrinus asterius (Pl. XII. 
figs. 18, 21); and the muscular unions of the remaining calyx- and arm-joints are so very 
_close that there is hardly any external character by which the syzygy between the two 
outer radials may be detected. Its presence is evident enough between the two joints 
following each axillary, as they are shorter than their successors. But nothing of this 
kind appears in the case of the radials, and as they are very apt to become shghtly 
separated at the edges I have found it almost impossible, especially in dry specimens, to 
determine the real nature of the union without separating the joints. This was done 
by Sir Wyville Thomson, whose preparations are figured in Pl. XI. figs. 15-25. 
The basals of Pentacrinus asterius are of very variable size, like those of Pentacrinus 
decorus, though not to the same extent. They are sometimes small, rounded knobs, not 
meeting one another upon the exterior of the calyx; or larger and more prominent, 
meeting their fellows in the re-entering angles beneath the radials ; but they never form 
a completely closed ring of triangular or pentagonal plates flush with the radials, as they 
do in Pentacrinus wyville-thomsoni, Pentacrinus alternicirrus, and some other species 
(Pl. XVIII. figs. 1-3; Pl. XIX. figs. 1, 6,7; Pl. XX. figs. 2, 3; PI. DEX): 
Liitken, Thomson, and others have endeavoured to establish as one of the characters 
of Pentacrinus asterius that the nodal joints of the stem are low and simple, while those 
of Pentacrinus miilleri and Pentacrinus decorus are thick and double, consisting of two 
parts united by syzygy. This is not really the case, however. In all recent Pentacrinidee 
the nodal joints proper, @.e., those which are pierced by the canals lodging the cirrus- 
vessels, are always single and united by syzygy to those next below them. But the line 
of junction is sometimes so nearly obliterated as to be only visible with difficulty ; while 
in other cases, such as Pentacrinus asterius (Pl. XIU. fig. 8), it is hardly distinguishable 
from the ordinary junction lines between the internodal joints, which are crenulated 
much less than usual. 
The following may therefore be regarded as the special marks of Pentacrinus asterius:— 
a robust stem with long internodes and wide cirrus-sockets; the ray-divisions rather 
irregular in number and grouping ; the projections of the pinnule-joints. 
Little is known about the range of Pentacrinus asterivs, either in depth or in space. 
Examples have been obtained off Barbados, Guadeloupe, Martinique, Montserrat, Nevis, 
and Saba Island; while the only two cases in which the depth is known with certainty 
are respectively 120 and 320 fathoms. Like the three other West Indian species, it is 
not known to occur out of the Caribbean Sea. 
(4oOL. CHALL. EXP,—PART XXXII, —1884.) 39 
