790 THE CRINOIDEA CAMERATA OF NORTH AMERICA. 



cup; the interradial spaces depressed and wider than usual in this genus; 

 they are composed of four phites, of which the three of the first row rest 

 upon the radials, their sides touching the distichals, the other being much 

 larger and interposed between the radial dome plates. Orals verj irregular 

 in their arrangement; the posterior one strictly central, very large and 

 spinous ; the others nearly flat, the position of the anterior one strictly inter- 

 radial, while that of the two antero-lateral ones appears to be almost radial. 

 The covering pieces enter the calyx after the first division of the ambulacra, 

 and the two branches are separated by a rather large plate. The anal open- 

 ing occupies the upper part of a well defined protuberance, a sort of rounded 

 vertical ridge, which extends from the special anal jjlate to the posterior 

 oral, and is surrounded by a deep groove. 



Horison and Locality. — Upper part of the St. Louis group, at Tateville, 

 Pulaski Co., Ky., associated with the preceding species. 



Types in the collection of Wachsmuth and Springer. 



Talarocrinus simplex (Shum.). 

 FlaU LXXVIII. Figs. 8a, h. 



1857. Bichocrhms simplex — Shumard; Trans. St. Louis Acad. Sci., p. li, Plate 1, Figs. %a, 6. 



1858. Dichocrinus simplex — Hall; Geol. Rep. Iowa, Vol. I., Part II., p. 654, Plate 22, Figs. 12a, {. 

 1882. Dichocrimis simplex — W. and Sp. ; Revision Palieoor., Part II., p. 8i. 



A small species, the width of the calyx varying from 5 to 9 mm. Dorsal 

 cup generally a little higher than wide, widest at the basi-radial suture or 

 a little above, somewhat cylindrical along the median portions, and gradually 

 contracting toward the arm bases. Plates thick, and without ornamentation 

 or other markings ; suture lines distinct, but not grooved. 



Basal cup large, semiglobose, extending to fully one half the height of 

 the calyx ; the lower end slightly flattened, the central part excavated, 

 forming a narrow circular pit of considerable depth ; the salient angles at the 

 upper margin quite obtuse, the re-entering angles toward the anal plate and 

 anterior radial comparatively sharp. Eadials slightly differing in form, some 

 being wider than other.?, but all, as a rule, longer than wide and narrowest 

 at the top. The .superior faces of the plates are directed obliquely inward, 

 and the ends are but slightly truncated ; they are excavated to one half 

 their width by the facets which contain the costals and distichals. Anal plate 

 generally wider at the bottom than the radials, but narrower at the top. 



