PLATYCRINID&. 695 
laterally. Column observed to a length of 29 em. without showing cirri. 
The joints change rapidly from circular to elliptical, and in width from 7 mm. 
to 17 mm. within 40 mm. from the crown, and from 1 mm. to 3 mm. in 
length. Their outer margins are angular, and the middle portions covered 
with a transverse row of ill-defined nodes. 
Horizon and Locality. — Upper Burlington limestone and Keokuk group ; 
Indian creek, Montgomery Co., Ind.; Keokuk, Iowa, and throughout Ken- 
tucky, Tennessee, Illinois, and Missouri, at the same geological horizons. 
Type in the (Worthen) Ilinois State collection, Springfield. 
Kemarks. —In a paper on “Transition forms in Crinoids” (Proceed. 
Acad. Nat. Sci. Phila., 1878, p. 244), we made this and the preceding species 
varieties of P. sculptus. They agree so closely in the form of the dorsal cup, 
and in the style of ornamentation, that it is impossible to separate them 
unless the arms are preserved, and even these do not differ essentially except 
in number. We now rank them as full species, but believe that P. glyptus 
and P. Safford: are lineal descendants of P. sculptus. 
Platycrinus scobina M. and W. 
Plate LX VII. Figs. 14a, b. 
1861. Mszx and Wortnun; Proceed. Acad. Nat. Sci. Phila, p. 129; also Geol. Rep. Illinois, Vol. III., 
p- 466, Plate 16,-Fig. 9. 
1881. W. and Sp.; Revision, Part II., p. 75 (Proceed. Acad. Nat. Sci. Phila., p. 249). 
Syn. Platycrinus clytis— Haw, 1861; Prelim. Descr. New Spec. Crin., p. 4; also Boston Journ. 
Nat. Hist., Vol. VIL, p. 286; figured 1872, N. Y. State Mus. Nat. Hist., Bull. 1, Plate 24, 
Fig. 4, and Mem. Am. Mus. Nat. Hist., Vol. I., Part I., p. 2, Plate 3, Fig. 6. 
A small species. Dorsal cup basin-shaped, more than once and a half as 
wide as high, the radials slightly convex, especially below the facets, giving 
to the transverse section of the cup an obscurely pentangular outline, and to 
the interradial sutures a shallow angular depression. Surface of cup orna- 
mented with numerous small nodes or coarse granules, rather sharply 
elevated, closely set, and irregularly arranged, which produce a rasp-like 
appearance. 
Basals closely anchylosed, leaving no groove or mark; they form a 
rounded basin, which rises to two fifths the height of the dorsal cup; the 
column facet small, and almost on a level with the truncated lower face. 
Radials a little broader than lone 
g, widening somewhat upwards, and present- 
ing a subquadrangular outline; the superior faces almost straight, their 
outer ends being but very slightly truncated. Radial facets small, occupying 
