BATOCRINID^. 483 



at the anal side, and composed of but few, rather large j^ieces, 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. 



Tgpe in the Museum of Comparative Zoology. 



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 Am]?lioracrinus, but they 

 afterwards regarded it as the type of a new genus, for which they proposed 

 the name Splicerocnnus, which, being preoccupied by Roemer, was changed 

 into Codocrinus. 



Aoroerinus Cassedayi (Lyon). 



Plate XLII. Figs. 11a, I, and M. 



1860. Jetinocrimis Cassedayi — Lyon ; Proceed. Acad. Nat. Sci. Pliila., p. 410, Plate 4, Pigs 3, 3a. 

 1881. Genneeocrimts Cassedayi — W. and Sp. ; Eevisiou Pateocr., Part II., p. 161. 



(?) Syn. Actiiiocrims eauUctiliis — Hall; 15tli Rep. N. Y. State Cab. Nat. Hist., p. 132. 



(?) Syn. Actiiiocrinus calypso — Hall; 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 palraars 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. Eadials 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 i^lates, 

 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 



