oe THE CRINOIDEA CAMERATA OF NORTH AMERICA. | 
hidden. ‘The covering plates of the ambulacra proceed from the outer sides 
of the orals to the ends of the appendages; they are suturally connected 
throughout their full length, and-form, together with the plates of the dorsal 
side, almost rigid tubes. ‘Those of the disk are large, as long as wide, and 
their surfaces flat; those of the appendages in part are covered with strong 
nodes. The plate overlying the costals, from which the bifurcation of the 
ambulacra takes place, is large and nodose. It is succeeded by two rows of 
transverse plates of irregular size, of which the larger ones are crowned by 
nodes similar to those upon the orals, but more prominent, and with coarser 
markings; they are arranged transversely, like the plates bearing them. 
The larger plates are so disposed that there is one at the base of each 
arm, and by counting the nodes the number of the arms can be ascertained 
from them as readily as from the brachials. Between every two-nodal plates 
are two or three smaller ones, which are flat, except for the general curva- 
ture. Anus low down, facing laterally. Column large and long, rapidly 
twisting ; the proximal joint circular, the succeeding ones turning abruptly 
into elongate-elliptic — the long diameter twice the shorter one — and their 
longitudinal thickness increasing as they recede from the calyx. Each joint 
is twisted so that the long axes of its reverse faces make a considerable 
angle with each other; the other rim is beveled to an edge, from which 
small tooth-like spines proceed outward. The articular ridge well defined, 
and bordered at the sides by deep fosse. Axial canal extremely small. 
Horizon and Locality.— Transition bed between the Upper Burlington | 
and Keokuk beds; near Burlington and at Pleasant Grove, Iowa. Also in | 
the lower part of the Keokuk proper at Niota and Nauvoo, Il. 
Types in the collection of Wachsmuth and Springer. 
< ee 
| Eucladocrinus millebrachiatus var. immaturus W and Sp. 
Whe | 
fii} Plate LXXITI. Figs. 2, 3. 
es There occur at Burlington in the same bed with Eucladocrinus miile- 
( 
brachatus very much smaller specimens, which are so closely similar to that 
species that they may represent its younger form; but as no intermediate 
stages have been discovered, and the gap is rather wide, we deem it advis- 
able to place them at present as a variety under that species. The calyx in 
these specimens, of which we obtained five examples in excellent preserva- | 
tion, is much shorter than wide, the dorsal cup saucer-shaped, the basal disk | 
