270 Fiztp CoLumBI1AN MuseEum—GeEo toey, VoL. II. 
ent enough in the figures, but which may possibly be due to indivi- 
dual variation, or abnormal development. The form and distribu- 
tion of the compound radials differ from those observed in any of 
the other genera of this group in the presence of two large plates 
underneath the superior part of one radial, so that we have appar- 
ently three infer-radials, with only two super-radials. The space 
occupied by one of these in the calyx wall is enough to account for 
the lateral bulging which gives its unsymmetrical form. Having 
but the one specimen, we cannot tell whether this feature is constant 
or not, and the specific and generic definitions do not depend upon 
it. As asymmetry is a frequent character in this group, however, 
there is no inherent improbability that the same construction will 
be seen in other specimens, if such are found. We give for compar- 
ison diagrams of Prsocrinus and Haplocrinus, the two genera nearest 
related to this structurally, (Pl. LXXXI, Figs. 7 and 8). 
Pisocrinus has two short super-radials, which rest upon one large 
infer-radial in common. Haplocrinus has three short super-radials 
each with its corresponding infer-radial. Our crinoid has two short 
super-radials, one connected by a transverse suture with its infer- 
radial, while the other is angular below, and meets the upper sloping 
faces of the two infer-radials. If now we examine the diagram of 
Haplocrinus (Fig. 8) we will see that the right anterior super-radial 
is angular below, and meets by one side an upper sloping face of the 
infer-radial below it, and by the other a corresponding sloping face 
of the anterior radial, which is one of the two largest plates in the 
calyx. Ifa portion of this anterior radial were cut off by a curving 
suture, as indicated by the dotted line in the diagram, it would give 
a construction substantially the same as that of our genus in this 
respect, viz: two short super-radials supported by three infer-radials. 
In view of the other pronounced differences in the composition of: 
the calyx, such a modification of the radial structure of Haplocrinus 
may well have become constant in our form. 
A few of the arm plates have fallen in over the summit of the cup, 
and are thus preserved. They are restored to position in the diagram 
(Fig. 6). The first brachial of the left posterior ray 1s wanting, but 
jts position is indicated by dotted lines. It will be observed that 
the right posterior radial has a smaller facet, and bears a smaller 
arm than the others. It is probable that the arms were very short, 
with but few more brachials than remain in the right anterior ray. 
We cannot be absolutely certain that the orientation of the calyx 
here given is correct, as we do not know the position of the anus. 
It agrees with what we know of the relative positions of the com- 
