148 THE CRINOIDEA CAMERATA OF NORTH AMERICA. 
the radial symmetry, but the bilateral as well, and strongly suggest that 
the Crinoids had to wrestle for a long time with the tendencies derived from 
their Cystid antecedents, manifesting themselves in a variety of irregular- 
ities, which from time to time characterized special groups. Such are the 
presence of compound radials in one or more rays; the variations in the 
form and composition of the proximal ring in the base; the non-arm bearing 
radials of Baerocrinus, Atelestocrinus, and Tribrachiocrinus ; the irregular 
number of radials — more or less than five — of the Plicatocrinide; and 
the almost complete obliteration of symmetry among the Pisocrinide and 
Calceocrinide. 
The division of the Crinoids into two orders: “ Palseocrinoidea” and 
“Stomatocrinoidea” was proposed by us on account of the apparent differ- 
ence in the conditions of the actinal portions of the calyx, whereby mouth 
and food grooves, and the ventral disk generally, of all Paleozoic Crinoids, 
without exception as we supposed, was covered by a special integument — 
the “vault” of antecedent literature — instead of being external and exposed 
to view. With the knowledge we then had this seemed to be a character 
morphologically of extreme importance, and it was so regarded by others. 
Under the order Palxocrinoidea we placed all Crinoids with covered mouth 
and closed food grooves, and under the Stomatocrinoidea those in which 
mouth and food grooves are exposed. The two groups were accepted by 
Carpenter, but he changed the name of the latter into “ Neocrinoidea.” 
Another classification was introduced by Neumayr,* who proposed the 
name “ Hypascocrinoidea” for all Crinoids in which mouth, ambulacral 
vessels, and Sawmplittchen (the latter if present) are beneath the tegmen; 
and the “ Epascocrinoidea” for those forms in which the ambulacra are not 
covered by the tegmen, but have external grooves, which are either exposed 
or closed by movable Sawmpliittchen. Under the latter he arranged all recent 
Crinoids with our Fistulata; under the former the Ichthyocrinidx and Haplo- 
crinids together with our Camerata. It is surprising that Neumayr’s classi- 
fication, while based like ours upon the condition of the mouth and surround- 
ing parts, led to such different results. This must be attributed largely to 
the interpretation which he gave to the disk of Cyathocrinus, in which he 
took the vacant space found in the centre of imperfect specimens for the 
mouth, and to the fact that he was unacquainted with the ventral structure 
of the Ichthyocrinide. 
* Die Stamme des Thierrejches, 1889, p. 462. 
