8 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 93 



DISCOCYSTIS Gregory, 1897 



{Echinodiscus Worthen and Miller, 1883 (not Agassiz) ; 

 Ageladisciis Miller, 1897) 



Like Agelacrinites except that four ambulacra are curved to left 

 and one, the right posterior (5), to right, and that body is well de- 

 veloped and sacklike with many rows of elongate, narrow marginal 

 plates. 



Genotype. — Echinodiscus optatus Worthen and Miller, 1883 = !). 

 (Agelacrinus) kaskaskiensis Hall, 1858. Mississippian of Illinois. 

 Echinodiscus sampsoni Miller, 1891, is another species of this genus. 



COOPERIDISCUS, n. gen. 



Body depressed globular, free, entirely covered with plates ; ambu- 

 lacra long, very narrow, much curved, all turning to the right. Inter- 

 ambulacral plates strongly imbricate. Anal pyramid of regular tri- 

 angular plates meeting at a point. 



Genotype. — Lepidodiscus alleganiiis Clarke, 1901. Devonian (Che- 

 mung) of New York. 



LEPIDODISCUS Meek and Worthen, 1868 



Like Cooperidiscus but ambulacra 1-4 curve strongly to the left and 

 5, the right posterior one, to the right. Literambulacral plates small, 

 strongly imbricating. Anal pyramid well developed. 



Genotype. — Agelacrinites squaniosus Meek and Worthen, 1868. 

 Mississippian. Agelacrinites heccheri Clarke, 1901, A. buttsi Clarke, 

 1901, Lepidodiscus Ichouri Sladen, 1879, and L. milleri Sharman and 

 Newton, 1892, are the known species of this genus. 



ULRICHIDISCUS, n. gen. 



Body semiglobose with the oral side occupied by five narrow but 

 well-defined, very long ambulacra all strongly curving to the left, 

 with a well-defined anal pyramid of many long triangular plates in 

 one circle, and interambulacral areas composed of polygonal but 

 slightly imbricating plates. 



Genotype. — Agelacrinus pulaskicnsis Miller and Gurley, 1894. Mis- 

 sissippian (Chester) of Kentucky. 



Family EDRIOASTERIDAE Bather ^ 



Theca flexible, depressed, usually globular, attached by the small 

 central excavated parf of the aboral surface ; ambulacra strongly 



