702 THE CRINOIDEA CAMERATA OF NORTH AMERICA. 
two palmars with two arms to the inner. Arms cylindrical, very stout for 
the size of the species, and not tapering except at the tips; their plates 
short. Pinnules strong and closely set, the joints three to four times as long 
as wide. Structure of the ventral disk unknown. 
Horizon and Locality. — Lower Burlington limestone, Burlington, Iowa. 
Type destroyed in the great Chicago fire. 
_ Lemarks. —'The ornamentation of this species is very variable, as shown 
by the illustrations. In some specimens the entire surface of the plates is 
covered with small but distinct nodules, in others the nodules are confluent 
and the surface appears to be coarsely granulated ; still others have irregu- 
lar larger nodes at the median portion of the radials. The basal disk is also 
flatter in some specimens than in others. 
Platyerinus Wortheni Ha t. 
Plate LXVIT. Fig. 9. 
1858. Hain; Géol. Rep. Iowa, Vol. I., Part II., p. 580, Plate 8, Fig. 4. 
1881. W. and Sp.; Revision, Part IT., p. 76 (Proceed. Acad. Nat. Sci. Phila., p. 250). 
Of medium size. The species is of the type of P. perasper, and has a 
similar ornamentation ; but the dorsal cup is more elongate, the nodes upon 
the plates are less regular, and angular instead of rounded ; also the basal 
disk is proportionally larger, the radials longer and more erect, and each 
half of the rays has four to five arms instead of three. Dorsal cup cup-shaped, 
angular along the interradial sutures, and truncate at the base; its whole 
surface densely covered by prominent granules or subspiniform nodes, 
Basal disk concave; sharply pentagonal; the extreme outer margins on a 
level with the lower edges of the radials; the proximal stem joints circular. 
Radials as long as wide at the upper end, subquadrangular, the lower faces 
truncated, the sides very little expanding upwards. Facets wide and deep, 
surrounded by a projecting rim, the upper margin broadly excavated. Basi- 
radial and interradial sutures slightly grooved, the interbasal sutures obso- 
lete. Costals small, trigonal, wider than long. Distichals short, more than 
twice as wide as long, and the first, as well as the second, resting within the 
facets, their inner faces suturally united, as also those of the palmars. The 
plates of the two succeeding orders of brachials are but slightly smaller than 
the distichals, and the second plate of each order, as in the case of the dis- 
tichals, is wider than the first. Arms eight to ten to the ray, rather stout, 
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