542 



NORTH AMERICAN INDEX FOSSILS. 



138. A. conicus Lyon and Casseday. Mississippic. 



Dorsal cup so flat as to be almost invisible from side view. 

 Keokuk of Kentucky, Tennessee and Indiana. 



XLVIII. EuTROCHOCRiNUS Wachsmuth and Springer. 



Calyx wheel-shaped. Dorsal cup narrow to the top of the 

 radials, thence spreading abruptly at right angles to the axis of the 

 calyx. Tegmen almost flat to near the base 

 of the anal tube, B 3, equal. R larger than 

 both costals together. Arm openings equi- 

 distant. Arms single or in pairs, biserial, 

 very short and incurving. Anal tube stout, 

 central and long. Column round. Missis- 

 sippic. 



139. E. christyi (Shumard). (Fig. 1871.) 



Mississippic. 



Plates of dorsal cup flat, of tegmen convex. 

 (Type of genus.) 



Characteristic of Upper Burlington of Mis- 

 souri, Illinois and Iowa. 



XLIX. DizYGOCRiNus Wachsmuth and 

 FIG. 1871. Eutro- Springer. 



chocrinus christyi, X Vz- Ventral disk usually as high as dorsal cup, 

 (After Meek and Worth- goj^^times much higher. Plates smooth, gran- 



en, 111. Geol. , V . ) ° 



ular, or obscurely striated. B very short, 



forming a slightly projecting circular rim or shallow basin. 

 R shorter than in Batocrinus. Upper brachials usually in a con- 

 tinuous ring around the calyx. Arms long and biserial, single or 

 in pairs. Anal tube short, slender, almost central. 



Differs from other known genera except Eutro chocrinus and 

 Dorycrinus in the tendency of the arms to multiplication. Mis- 

 sissippic. 



140. D. rotundus (Yandell and Shumard). Mississippic. 



Calyx ovate to depressed, globose (about one inch wide). Plates 

 flat, with perfectly smooth surface and indistinct sutures. Arms 

 18 to 22, usually 20. 



