436 THE CRINOIDEA CAMERATA OF NORTH AMERICA. 
far as observed, of uniform size. To a length of about two inches the joints 
are of equal length, and there are no internodal joints. But when the latter 
make their appearance, they increase rapidly to seven to the internode, which 
seems to have been the maximum number. The upper joints, and the nodal 
ones below, are rounded at their edges, and project conspicuously beyond the 
sides of the intervening ones. 
Horizon and Locality. — Keokuk limestone ; White’s Creek Springs, near 
Nashville, Tenn.; Button Mould Knob, Ky.; Keokuk, Iowa, and Warsaw 
and Nauvoo, Ills. | 
Types in the (Worthen) IHinois State collection, Springfield. 
Lobocrinus Nashville var. subtractus (WuirTer). 
Plate XX XI, Figs. Za, 6. 
1862. <Actinocrinus Nashville var. subtractus — Wuite ; Proceed. Bost. Soc. Nat. Hist., Vol. IX., p. 16. 
1881. Batocrinus Nashville, var. subtractus — W. and Spr.; Revision Paleocr., Part II., p. 167. 
This variety differs from the typical form in being less strongly lobed at 
the arm regions, and in having no spines upon the anal tube. The plates of 
the tube are but slightly convex, and each one is surmounted by a small 
conical protuberance in the centre. It also differs in the structure of the 
stem. In specimens from the Burlington limestone, and Burlington and 
Keokuk Transition bed, the proximal stem joints are shorter than the suc- 
ceeding ones, and all have an angular edge; while in the specimens from 
the Keokuk limestone proper the edge is rounded. At three inches from 
the calyx, all stem joints are nearly of uniform size. 
Horizon and Locality. — Upper part of Upper Burlington limestone and 
Burlington and Keokuk Transition bed; Des Moines Co., Iowa ; Henderson 
Co., and Nauvoo, Ills. 
Remarks. — Dr. White gives the absence of the interdistichal piece as the 
principal distinction between the two forms; this, however, is not a persistent 
character. We have a number of specimens from the true Burlington beds 
in which that plate is represented in one or more rays. 
Lobocrinus robustus W. and Sp. (mov. spec.). 
Plate XXX. Figs. Sa, b. 
A large species. Calyx about as high as wide, deeply and broadly de- 
pressed between the rays. Dorsal cup but little higher than the ventral disk, 
the sides slightly convex, constricted at the basi-radial sutures. Plates almost 
flat and without ornamentation or other markings; suture lines somewhat 
grooved. 
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