PLATYCEINID^. 677 



SAB^ GROUP. 



The plates of the dorsal cup smooth or obscurely granulose ; the inter- 

 basal sutures raised into ridges by excessive secretion of calcareous matter 

 during anchylosation ; the stem with internodal joints. 



Platycrinus Sarse Hall. 

 Plate LXIX. Fig. 7, and Plate LXX. Fig. 1. 



1858. Hall; Geol. Rep. Io\¥a, Tol. I., Part II., p. 673, Plate IS, Kg. i. 

 1881. W. aud Sp. ; Eeyision, Part II., p. 74. 



Syn. Plati/criims Georgei,'B.AUL; Suppl. Geol. Rep. Iowa, p. 82. 



Syn. P. pmlleiuiHus M. and W. ; Geol. Rep. IlUnois, Vol. II., p. 264-, Plate 20, Kg. 2. 



Syn. F. moiiroensis Woethek; ibid., Tol. VII., p. 306, Plate 30, Kg. 9. 



Dorsal cup goblet shaped, gibbous in the middle, broadly truncate at the 

 base. Surface of plates smooth, or covered with a few obscure ridges passing 

 out from the facets to the lower angles of the radials. 



Basals forming a saucer-shaped dish, occupying fully one third the height 

 of the dorsal cup ; the lower end broadly truncated, the outer margin pro- 

 jecting and forming a rim ; the lower face a little concave, and wider than 

 the upper stem joints. Interbasal sutures distinctly elevated above the gen- 

 eral surface, and formed into ridges. Radials quadrangular, as wide as long, 

 and as wide at the lower end as at the upper. Facets deeply indented, em- 

 bracing the costal and one or both distichals. Costals very small, triangular. 

 Distichals once and a half as wide as long, giving off an arm to the outer 

 side of the plates, their inner sides two palmars with two arras, making six 

 arms to the ray. Arms biserial from the second or third joint, of moderate 

 size ; the tips somewhat tapering. Pinnules very long and closely set ; their 

 joints more than twice as long as wide. Structure of the ventral disk im- 

 known. Column very slightly oval ; composed of nodal and internodal 

 joints, the former wider and higher than the internodals. Whether the 

 upper and lower faces of the joints have transverse ridges could not be 

 ascertained from the specimens. 



Eorisoii and Locality. — St. Louis group ; St. Louis, Mo., and Jersey 

 Co., 111. 



Types in the (Worthen) Illinois State collection, Springfield. 



RemarJcs. — P. Sarm was described from a very large, somewhat crushed 

 specimen, showing indistinct traces of ornamentation ; P. Georgii from a dis- 



