WHITE.] CARBONIFEROUS FOSSILS. 127 
arms of one and the same ray; these interbrachial sutures being similar 
in aspect to those which separate the pieces composing the calyx. The 
pinnules of the arms are thus wholly obscured from view when the arms 
are closed. 
' The arms of this genus, as shown by our example of H. typus, are more 
nearly like those of Graphiocrinus de Konineck & Lehon than those of 
Enerinus Miller, although, as Mr. Meek pointed out (loc. cit.), it is in 
some respects closely related to the latter genus. 
ERISOCRINUS (CERIOCRINUS) PLANUS White. 
Plate 35, figs. 5a and 0. 
Brisocrinis planus White, May, 1880, Proc. U. 8. National Museum, vol. ii, p. 257. 
Body rather small, subcireular or obscurely pentahedral in lateral out- 
lines as viewed from above or below, shallow basin-shaped below the 
top of the first radial pieces; base rounded and somewhat deeply im- 
pressed at the middle, the depression gradually rounding outward to 
the sides; basal pieces very small, occupying the bottom of the depres- 
sion of the base, and almost covered by the first jomt of the column; 
subradial pieces moderately large, their inner ends inflexed by the de- 
pression of the base to meet the basal pieces at its bottom, their outer 
ends extending outward and upward, so as to be more or less plainly 
visible by side view of the body; first radial pieces comparatively large, 
convex vertically, their upper edges rounded inward to the suture be- 
tween them and the second radials, their lower angles extending down- 
ward almost to the lower surface of the body as it-is seen by side view. 
The other characters are those common to the genus. One minute piece 
remains attached to the upper border of the calyx of the example from 
which this description is drawn, at the junction of two of the first radial 
pieces. This is doubtless an anal piece, but it does not in any degree 
enter between the two posterior first radials upon the borders of which 
it rests, although it evidently rested betwen the two corresponding see- 
ond radials. 
Transverse diameter of the calyx, 14 millimeters; height of the same, 
5 millimeters. 
This species differs from ZH. typus in having a shallower and more 
rounded, basin-shaped calyx, proportionally smaller basal and larger 
subradial pieces, a more deeply impressed base, and, also, in possessing 
the minute anal piece before described. It very closely resembles the 
Poteriocrinus hemisphericus of Shumard, examples of which are associ- 
ated with it in the collection from 30 miles west of Humboldt, Kans. 
Indeed, so far as the characteristics of the calyx alone are concerned, 
which are in part well shown by fig. 5¢, plate 35, there appears to be no 
essential difference except in the relative position of the small anal piece. 
In Lrisocrinus proper the anal series of pieces is entirely wanting, so 
far at least as their appearance at the outer surface is concerned. In 2. 
planus there is one small anal piece visible between the two posterior 
second radial pieces, but it does not extend downward between the two 
corresponding first radial pieces of the calyx. In this species, therefore, 
the calyx is precisely as it is in true Hrisocrinus. In the case of the 
form described by Shumard as Poteriocrinus hemisphericus, and also the 
Cyathocrinus inflecus of Geinitz, there is likewise a single anal piece; 
and it occupies the same relative position in both those forms that it 
does in #. planus, except that it is longer and extends downward be- 
tween the two posterior first radial pieces, as well as upward between 
a 
