BATOCRINID 2. 483 
at the anal side, and composed of but few, rather large pieces, among which 
the orals are well defined. The posterior oral is central, larger than the 
surrounding ones, and more convex. The anus opens out obliquely upwards. 
Horizon and Locality. — Lower Burlington limestone ; Burlington, Iowa. 
Type in the Museum of Comparative Zodlogy. 
Remarks. — This species is readily distinguished from allied forms by the 
concavity of the basals, the curvature and extremely large size of the radials, 
the vertical position of the fixed brachials, and the flatness of the tegmen. 
It was at first referred by Meek and Worthen to Amphoracrinus, but they 
afterwards regarded it as the type of a new genus, for which they proposed 
the name Spherocrinus, which, being preoccupied by Roemer, was changed 
into Coelocrinus. 
Aorocrinus Cassedayi (Lvov). 
Plate XLIL, Figs. 11a, 6, and 12. 
1860. Actinocrinus Cassedayi — Lion ; Proceed. Acad. Nat. Sci. Phila., p. 410, Plate 4, Figs 3, 3a. 
1881. Genneocrinus Cussedayi —W. and Sp.; Revision Paleocr., Part II., p. 161. 
(2) Syn. Actinocrinus cauliculus —Hati; 15th Rep. N. Y. State Cab. Nat. Hist., p. 132. 
(?) Syn. Actinocrinus calypso — Hau; ibid., p. 133. 
Calyx small, width across the arm bases slightly exceeding the height, 
broad at the bottom, constricted at the basi-radial sutures; the interradial 
spaces deeply indented at the arm regions, especially at the anal side, which 
gives to the distichals and palmars the appearance of arm plates. Plates of 
the dorsal cup strongly convex, the surface covered with radiating ridges, 
which enter only the margin of the plates. 
Basals large, short, forming a broad rim with sharp marginal edges, which 
are notched at the sutures; the lower face a little concave, and the median 
part somewhat excavated for the reception of the column. Radials com- 
paratively large, but smaller than the basals; wider than long. First costals 
about half the size of the radials; the second generally smaller than the first. 
Distichals 2 X 10, the upper axillary and followed by two rows of palmars ; 
the latter, as well as the distichals, curved like arm plates, and projecting con- 
spicuously over the interradial spaces. Arms twenty, four to each ray. In- 
terbrachials four to six; two in the second row, two or three in the third, and 
two between the arms, the latter connecting with the interambulacral pieces. 
Anal interradius considerably wider; the first anal followed by three plates, 
all somewhat smaller than the first interbrachial of the other sides; and these 
by a large number of minute, irregular pieces, forming a rounded, almost 
