688 THE CRINOIDEA CAMERATA OF NORTH AMERICA. 
circular, occupying one third the width of the plates. Costals subtrigonal, 
the sloping upper faces concave, and their angle rather sharp. Distichals 
and palmars once and a half as wide as long. Arms from six to eight to the 
ray, of nearly uniform size throughout, biserial from their fourth or fifth 
plate ; the joints moderately long, united by slightly waving sutures. Pin- 
nules strong, composed of long joints. Structure of ventral disk unknown. 
Horizon and Locality. — Upper Burlington limestone, Burlington, Iowa. 
Type in the Museum of Comparative Zodlogy. 
ftemarks. —In this species Meek and Worthen included another form, 
which we have described under the name of Platycrinus nodostriatus, and 
which differs essentially in the form of the basal cup, and in the style 
of ornamentation. 
Platycrinus brevinodus Hatt. 
Plate LXX. Figs. 2, 5, 6a, b. 
1861. Haut; Deser. New Spec. Crin. p. 4, and Bost. Journ. Nat. Hist., p. 286; figured 1872, N. Y. State 
“Museum, Bull. 1, Plate 2.4, Fig. 5. | 
1881. W. and Sp.; Revision, Part II., p. 70 (Proceed. Acad. Nat. Sci. Phila., p. 244). 
A rather small species. Dorsal cup nearly twice as wide as high, slightly 
spreading, broadly truncate at the base. Basals proportionally large, disk- 
like, truncate below, only the extreme upper ends turning upwards, very 
little concave, and the outer margins surrounded by a row of conspicuous 
nodes, directed outward and giving to the edges a crenulated outline ; the 
interbasal sutures obsolete. Radials wider than long, a little widest at the 
top; subquadrangular; the outer ends of the upper face but slightly sloping, 
except those of the anal side, which form a distinct notch, and support a 
rather large hexagonal plate. Radial facets shallow, occupying half the 
width of the plates. Basi-radial and interradial suture lines grooved. Cos- 
tals triangular, moderately large, occupying the whole width of the facets. 
Distichals two, free from the costals up, the first once and a half as wide as 
long ; the second as long as wide. Palmars, when present, but little larger 
than the succeeding arm plates. Arms four to six to the ray in the same 
specimen, rather slender and tapering; their proximal ends composed of five 
to six cuneiform pieces, which gradually turn into biserial above. Pinnules 
placed somewhat distant. Structure of ventral disk unknown. 
Horizon and Locality.— Described from the Keokuk group at Keokuk, 
Iowa; but occurring also at the same horizon at Indian creek, Montgomery 
Co., Ind., and in the Burlington and Keokuk transition béds near Burlington. 
