196 THE CRINOIDEA CAMERATA OF NORTH AMERICA. 
reception of the first interbrachial, their lateral faces comparatively short. 
Costals smaller than the radials. Arms ten, long, slender, somewhat flattened 
on the back; the three proximal plates take part in the calyx, are curved 
like the free plates, and are but little larger. The first free brachial is rectan- 
gular, but the succeeding ones gradually turn into cuneate, interlock, and 
finally change to biserial, with the upper and lower faces parallel. Pinnules 
long and closely packed. Interbrachials: 1, 2, 2. Anal side wider, the 
plates in three ranges, divided by a vertical row of anal plates; the lower 
one of the same size as the radials; the others smaller, decreasing in size 
upwards. Structure of the ventral disk, and form of the anus, unknown. 
Column pentangular. 
Horizon and Locality. — Niagara group; Lockport, N. Y. 
Remarks. — Our description and figure are made from Hall’s typical 
specimen * in the American Museum of Natural History, New York, after 
clearing away the matrix, which brought to light the pinnules and exposed 
the calyx plates. That Glyptaster is generically identical with Thysanocrinus, 
nobody will doubt after comparing our figure (Plate XVIII. Fig. 7) with that 
of Thysanocrinus liliiformis (Plate XVIII. Fig. 4). 
(2?) Thysanocrinus Halli (Lyoy). 
Plate XII. Figs. 9a, b. 
1861. Rhodocrinus Halli — yon ; Proceed. Acad. Nat. Sci. Phila., p. 412, Plate 4, Figs. 5a, 0. 
1ssl. (2) Rhodocrinus Halli — W. and Sr. ; Revision Paleocr., Part IL, p. 212. 
A large species. Calyx vasiform, a little wider than high, rounded below, 
the sides convex; the interradial spaces slightly flattened, and the radial 
plates rather sharply elevated, which gives to the cross-section a subpentan- 
gular outline. Surface of the plates smooth, the suture lines distinct but not 
channeled. 
Infrabasals visible beyond the column; the columnar attachment large, 
circular, its outer margin surrounded by well-defined radiating stria. Basals 
large, a little convex; four of them pentangular or nearly so, the upper 
angles almost meeting the interbrachials, sometimes slightly touching them ; 
the fifth plate pentangular, broadly truncate above. Radials and costals 
wider than high, gradually decreasing in size upwards. Of distichals only 
two are preserved, and only in one division of two of the rays. There are only 
* Figured by Hall. New York Paleont., Vol. Il., Plate 41, Vig. 4. 
