oeiNoiDS. J 97 



Platycrinus discoideus Owen & Suumard. 



Platycrinus discoideua Owen & Shumard, 1850 : Jour. Acad. Nat. Sci., Phlla., 

 (2), vol. ir, p. 58, pi. vii, tig. 1. 



Plaiycrinus discoideus Owen & Shumard, 1852 : Geol. Sur. Iowa, Wis- 

 consin and Minnesota, p. 588, pi. vA, tigs. la-b. 



Platycrimis multibrachiatus Meek & Worthen, 1861: Proc. Acad. Nat. Sci., 

 Phila., p. 134. 



Platycrinus excavatus Hall, 1861 : Boston Jour. Nat. Hist., vol. VII, p. 286. 



Platycrinus gorbyi Miller, 1891 : Geol. Sur. Missouri, Bui. 4, p. 15, pi. i, 

 tig. 14. 



Platycrinus pulchellus Miller, 1891: Geol. Sur. Missouri, p. 11, pi. i, fig. 7. 



P;aifyc?-mMs cawMs Hall, 1853 : Geology Iowa, vol. I, p. 527, pi. viii, figs, 

 la-b. 



Crown large, spreading. Calyx broad, depressed. Dorsal 

 cup basin-shaped, very shallow ; basals forming a flat, penta- 

 gonal disk, radials broad, often slightly protuberant at the arm 

 bases. Ventral side low, hemispherical. Arms stout. Orna- 

 mentation quite variable, usually made up of nodes and gran- 

 ules, which frequently are confluent, forming concentric rows 

 around the arm bases and column ; arms also covered with 

 granules and small wrinkles. 



Horizon and localities. — Lower Carboniferous, Lower Bur- 

 lington limestone: Hannibal, Louisiana, Sedalia. 



Platycrinus discoideus is a very variable form, as may be infer- 

 red from the specific names it has received. It was one of the 

 first species of the genus recognized in the Mississippi valley. 

 P. gorhyi and P. pulchellus, recently described by S. A. Miller, 

 appear to belong to Owen & Shumard's type. At Burlington, 

 Iowa, where the original specimens were found, variations as 

 great as is represented by these two forms are to be noted, 

 with a complete series of intergradations. 



Platycrinus subspinosus Hall. 



Platycrinus subspinosus Hall, 1858: Geology Iowa, vol. I, p. 536, pi. viii., 



figs. 9, 10. 

 Platycrinus subspinosus Meek & Worthen, 1866: Geol. Sur. Illinois, vol. 



II, p. 173, pi. XV, fig. 6. 

 Platycrinus subspinosus Meek & Worthen, 1873: Geol. Sur. Illinois, vol. 



V, p. 452, pi. xi, fig. 2. 

 Platycrinus occidentalis Miller, 1890: Geol. Sur. Missouri, Bui. 4, p. 10, 



pi. i, fig. 56. 



