522 NORTH AMERICAN INDEX FOSSILS. 



XXX. Talarocrinus Wachsmuth and Springer. 

 Calyx small, usually higher than wide. Plates thick and unor- 

 namented. Differs from Dichocrinus in its more massive plates 

 and in having but one costal to a ray ; and from Pterotocrinus in 



Fig. 1846. Dichocrinus inornatus, X Fig. 1847. Talarocrinus cornigerus. 

 ^. (After Wachsmuth and Springer.) (111. Survey.) 



its small distichals, free from the calyx and in the absence of wing- 

 like appendages. Mississippic (probably restricted to Warsaw and 

 St. Louis). 



74. T. cornigerus (Shumard). (Fig. 1847.) Mississippic. 

 Ventral disk highly elevated. Plates of radial dome strongly 



tuberculosa Posterior oral, simple and very large, forming a large 

 , ovate tubercle. 



St. Louis of Alabama and Kentucky. 



75. T. simplex (Shumard). Mississippic. 

 Small (width of calyx not exceeding one third of an inch). 



Basal cup half the height of the calyx. Structure of arms and 

 ventral disk unknown. 



Warsaw of Kentucky, Tennessee, Indiana and Missouri. 



XXXI. Pterotocrinus Lyon and Casseday. 

 Plates heavy and smooth. Dorsal cup wider than high. Ventral 

 disk pyramidal, higher than the cup, and with 5 very large and 

 conspicuous plates arranged radially and passing out between the 

 arms, like wings or horns. B 2, five-sided, followed by 5 R and 

 an anal. Costals one to the ray. Arms 20 and short, in groups of 

 four. Column round. Mississippic (restricted as far as known to 

 Kaskaskia of North America). 



