596 NEW SPECIES OF CRINOIDEA, 
inwards superiorly ; inferior angles slightly salient. Superior plates unknown. Of the accessory picces, 
one plate only remains: this is nearly square, and is placed between the two heptagonal plates of the 
second series. 
Column very small, consisting of round joints, with articulating surfaces striated in radii. 
Dimensions.—Height of first series, 1 line; of second series 3-5 lines; greatest width of calyx, 5 
lines ; diameter at base, 2 lines. 
From the imperfect condition of the only specimen we have seen of this species, its characters shina 
be well determined; the description given above, however, will enable any one to identify it without 
difficulty. . 
It was found in the pentremital layers of the carboniferous limestone at Chester, Illinois, associated 
with Pentremites florealis, P. Cherokeus, Agassizocrinus dactyliformis, and Productus Flemingti. 
EXPLANATION OF FIGURES. 
a ss a. Basal vi 
. View of ii side. 
POTERIOCRINUS SPINOSUS. (N. 8.) 
(Tab. V. 8, fig. 4.) 
Calyx.—Cup-shaped, small; plates smooth; mouth proboscidiform ; arms five ; subdivisions thirty, 
furnished with thorn-like projections at the points of bifurcation. Basal plate pentagonal, small, slightly 
concave, with a minute pentagonal opening in the centre; divisions of the plate not perceptible. First 
series of plates pentagonal, small, thin. They surround the basal plate, and form by their union a little 
pentagon, flat or slightly concave, which is almost completely hidden from view by the last joint of the 
column, so that, in order to obtain a good view of them, it is necessary to remove this portion of the 
animal. The second series consists of five pieces, three pentagonal and two hexagonal; they are larger 
and more massive than the plates beneath; surface moderately convex, inferior margins bent inwards to 
articulate with the plates of the first series. Superior or arm-bearing plates, wide, pentagonal, thick, 
moderately convex ; facet for the articulation of the arms, wide, situated on the upper edge of the plates, 
occupying their entire breadth. Accessory pieces three, irregular. 
The surface of the calyx exhibits a number of small indentations, one of which is situated at each of 
the angles of the second series of superior, and accessory pieces. 
Main arms five, each composed of a single joint, which is irregular, elongated and furnished with a 
thorn-like projection superiorly. The upper edge presents two oblique facets, supporting two hands, con- 
sisting of wedge-shaped joints, arranged in single longitudinal series. The number of joints in the diffe- 
rent hands varies from eight to ten. The superior ones are spinous, and each supports two fingers, one 
of which continues without further division to the summit, the other bifurcates several joints above its” 
origin. 
Proboscis long and slender, surmounted by three plates of a conical figure, joined together at their 
bases. 
Column unknown. 
The specimen figured was obtained from the Archimedal layers of the carboniferous limestone of Kas- 
kaskia, Illinois. It there occurs with Terebratula plano-sulcata, T. Roissyii, Pentremites florealis, P. 
pyriformis, P. Cherokeus (Troost), and Poteriocrinus (Zeacrinus) magnoliaformis (Troost). It — 
also in a similar geological position in Grayson County, Kentucky, where it was discovered by Dr. L 
Yandell, whose fine collection of Crinoids contains a very perfect specimen of this interesting paeieas. 
POTERIOCRINUS OCCIDENTALIS. (N. 8.) 
(Tab. V. 8, fig. 5, a, b.) 
Calg —Cup-shaped, increasing from the base to the summit, swelled in the middle ; transverse section 
— ¢ireular ; plates somewhat massive, smooth, slightly convex. First series of vlites five, irregularly 
pentagonal, Blossly adhering among themselves, bent upwards below to form the sides of a funnel-shaped 
