REPORT ON THE CRINOIDEA. 205 
axillaries, like those visible in the next youngest specimen (PI. IV.); whereas the hexa- 
gonal plates themselves are separated in this manner. 
Further, in nearly all Neocrinoids which have ten or more arms there are three 
radials. This is true of all the recent Crinoids except Metaerinus, which has a larger 
number, four or six; and the only fossil genus which has two radials is the aberrant 
form Plicatocrinus. 
In all the Neocrinoids, except de Loriol’s recently established genus Hudesicrinus, 
there is either a syzygy or a hgamentous articulation between the two outer radials ; and 
the existence of a syzygy in Holopus is therefore nothing unusual, though there is less 
evidence of its presence in the adult condition than is usually the case. But this is 
scarcely surprising when we remember the excessively intimate union of the first radials, 
of which no indication whatever is visible on the exterior of the calyx. Some individuals, 
however, exhibit distinct traces of a sutural line dividing the large axillary into two parts. 
Such a line is visible in the young specimen (PI. IV.) on all the axillaries of the trivium, 
crossing them at the point where the medio-dorsal ridge bifurcates as described above ;* 
but it is less distinct in the two bivial axillaries. On the other hand, the three trivial 
axillaries of the large American specimen present’ no indications whatever of being 
composite joints, and have a regular; broadly pentagonal shape. This is well shown in 
Pl. I. fig. 2; but the bivial axillaries represented in fig. 1 are of an entirely different 
character, each of them being distinctly in two parts, which look as if they were 
articulated rather than suturally united, while they do not present the symmetrical 
appearance characteristic of the corresponding parts in other Crinoids. 
In the one case there is a large and wedge-shaped second radial which has all the 
appearance of an ordinary brachial. It supports a triangular axillary, but the apposed 
faces of the two do not: correspond exactly. The axillary extends beyond the narrower 
end of the second radial, and so comes in contact with the upward extension of the first 
radial already described. This is shown in Pl. I. fig. 1. The broader end of the second 
radial, however, extends considerably beyond the axillary, and meets not only the com- 
posite axillary of the adjacent trivial ray, but also the first brachial of its own ray as well 
as that of the next. 
The second radial of the other bivial ray, which is shown in the middle of PI. I. fig. 1, 
is more oblong than its fellow. Like it, however, it is wider than the roughly triangular 
axillary, and supports a considerable portion of the large first brachial. But it is not 
overlapped by the axillary at the other end, and completely cuts it off from the first 
radial below. 
None of the four remaining axillaries of the specimen figured in PI. II. show any 
distinct traces of their being of a composite character ;? though there are some lines upon 
1 These lines are not clearly seen in the positions of the specimen which are represented on Pl, IV. 
2 The lower angle of one of these exhibits an accidental fracture. 
