REPORT ON THE CRINOIDEA. 163 
principal vault pieces or interradials, as they were also called by Meek and Worthen.’ 
The grooves which converge upon it are not like those of Coccocrinus “which have 
no floor,” ? but they are formed at the sutures of the interradials, 7.e., the apposed edges 
of these plates are bevelled away so as to form a groove with the suture in the middle of 
its floor. 
According to Wachsmuth and Springer,’ the central space “in perfect specimens is 
completely covered by the apical dome plates. The food-groove and ambulacral canal 
are also arched over solidly by two rows of alternate plates which connect with the 
movable covering of the arm furrow.” The existence of these marginal alternating 
plates has yet to be proved in Coccocrinus, and until this has been done, the resemblance 
between this type and Cyathocrinus does not seem to me to be very “close,” for while 
the arm-grooves of Cyathocrinus are continued towards the peristome over the united 
edges of the interradials, this is by no means the case in Coccocrinus; and there is no 
groove on the ventral disk at all, any more than there is in Holopus, or in any young 
Crinoid before the separation of the orals and radials by the expansion of the equatorial 
zone. The fact that the principal vault pieces of Coccocrinus are not united laterally, as 
is the case in Cyathocrinus, seems to me to be one of very considerable morphological 
importance. It must of course be remembered, as Wachsmuth has pointed out in other 
cases, that the absence of a covering to the central space and its radial clefts in the fossil 
Coccocrinus is no proof that it was not present during life as in Cyathocrinus. But the 
two genera are not in the same morphological condition, and all that we know about 
Coccocrinus goes to indicate its resemblance to Holopus with open slits between the 
orals and an uncovered mouth. Wachsmuth,* however, states that he has “yet to 
discover a single palzeozoic genus in which a special oral aperture has been identified, or 
in which the existence of a solid vault has been disproved, or cannot be traced by 
analogy.” I believe, on the contrary, that the special oral aperture is to be found in 
Coccocrinus as in Holopus, and that it is pushing analogy too far to assert the existence 
of an as yet undiscovered vault in this genus. 
If then, as I believe, there was an unobstructed mouth in Coccocrinus as in Holopus, 
I cannot agree with Zittel’s association of this type with Haplocrinus, which had a closed 
oral pyramid. 
Wachsmuth and Springer’ place Coccocrinus near Platycrinus. “The two genera 
are identical in the construction of the calyx, and the summit really forms the only 
distinction between them.” To this point I shall return, Coccocrinus, like the recent 
Holopus, seems to me to be permanently in the condition of a Crinoid larva in which the 
orals have not yet moved away from the radials, though separated from one another. 
Haplocrinus and Symbathocrinus are permanently in the condition of an unopened 
1 Paleontology of Illinois, vol. v. pl. ix. fig. 13. 2 Revision, part ii. p. 58. 
3 Revision, part i. p. 84. * Amer. Journ. Sci. and Arts, vol. xiv. p. 190. 5 Revision, part ii. p. 58. 
