196 THE CRINOIDEA CAMERATA OF NORTH AMERICA. 



reception of the first interbrachlal, 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 XYIH. Fig. 7) with that 

 of TliysanoGrinus liliiformis (Plate XYIH. Fig. 4). 



(?) Thysanocrinus Halli (Lyon). 

 Plate XIII. Figs, 9a, h. 



1861. R^odocrimis Halli — Lyon ; Proceed. Acad. Nat. Sci. Pliila., p. 413, Plate 4 Kgs. ^a, b. 

 1881. (?) nhodocrinus Halli — 'W. and Sp. ; Revision Palgeocr., Part II., p. 212. 



A large species. Calyx vasiform, a little wdder than high, rounded below, 

 the sides convex; the interradial spaces slightly flattened, and the radial 

 plates rather sharply elevated, wdiich 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 striae. 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. Eadials and costals 

 wider than high, gradually decreasing in size upw^ards. Of distichals only 

 two are preserved, and only in one division of two of the rays. There are only 



* Pigured by Hall. New York Pakont., Yol. II., Plate 41, Pig. 4. 



