THYSANOCRINIDE. 193 
a deep notch for the reception of the first interbrachials. Costals about of 
equal size, considerably smaller than the radials. Arms ten, rather stout, the 
two lower plates, which are included in the calyx, longer than the free plates ; 
the latter short, arranged in two series, with a few cuneate interlocking joints 
at the proximal end. Pinnules long, closely packed ; composed of about six 
remarkably long joints, which are thickest at the ends. First interbrachials 
as large as the radials; succeeded by two much smaller plates, and a few 
still smaller ones above. Anal plate large, resting upon the truncated basal ; 
succeeded by three plates in the second row. Structure of disk and position 
of anal opening unknown. Column round, strong, the nodal joints wider and 
longer, rounded at their edges. 
Horizon and Locality. — Niagara group ; Lockport, N. Y. 
Type in the Museum of Cornell University at Ithaca. 
Thysanocrinus inornatus (Harr). 
Plate X VIII. Figs. Ga, b, c, d, and XIX. Fig. 5. 
1863. @lyptaster inornatus —Hatn; Trans. Alb. Inst., Vol. IV., p. 2055 also 28th Rep. N. Y. State Mus. 
Nat. Hist. (1879, Ed. I1., p. 134), Plate 14, Figs. 1-6; also 11th Rep. Geol. Surv. Indiana, 
1881, p. 263, Plate 18, Figs. 1-6. 
1881. Glyptaster inornatus — W. and Sr.; Revision Paleoer., Part IT., p. 196. 
Calyx somewhat urn-shaped, the sides slightly convex ; cross-section at 
the top of the costals pentagonal, the angles corresponding to the rays; 
across the distichals decagonal. 
Infrabasals very minute, only the extreme points of the plates visible 
beyond the column.* The ornamentation consists of single series of broad, 
ill-defined radiating ridges or elevations. Some of the more prominent ones 
follow the median line of the rays; while others take a lateral direction, 
radiating from the centre of the plates to the margins, where they meet 
with similar ridges from the interbrachials and basals. 
Basals large, their lower margins thickened and expanded into nodes — 
one to each plate — which stand on a level with the top stem joint, and 
form a marked pentalobate rim around it. Radials larger than the basals, 
and wider than long. First costals considerably smaller and quadrangular, 
%* Prof. Hall described the “basals” —the infrabasals of modern terminology — as “much developed, 
distinctly pentangular, with a double or triple node on each plate, and spreading beyond the column.” From 
this description we suspect that the author took the nodes at the lower end of the dasa/s for plates, and over- 
looked the small infrabasals which are rarely observed. We draw attention to this, because Hall, in compar- 
ing this species with his “ Glyptaster” occidentalis, makes “the greater development of the basal plates” 
a specific distinction. 
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