BATOCRINIDiE. 427 



Dizygocrinus bitiirbinatus (Hall). 

 Plate XXXIII. Fig. 9. 



1858. Actmocrinus hiturbinatus — Hall; Geol. Eep. Iowa, Vol. I., Part II., p. 616, Plate 16, Figs. 5 and 



6^5, 5, c, 

 1873. Baiocriniis Uturbinaius — Meek and "Worthen; Geol. Rep. Illinois, Vol. V., p. 367. 

 1881. Batocrvius hiturbinatus — W. and Sp. ; Kevision PaliEOcr., Part II., p. 165. 



Sjn. Batocrinus lyonaims Millee and GuELEY, 189i ; Geol. SurT. Illinois, Bull. 3, p. 18, Plate 3, 



Pigs. 4 and 5. 



Calyx biturbinate, about as wide as high, the ventral disk as high as the 

 dorsal cup. Plates below the arm regions flat, above slightly convex, their 

 surface perfectly smooth ; suture lines indistinct. 



Basals small, forming a hexangular, shallow basin, with a slightly pro- 

 jecting rim at their lower margins. Radials once and a half as wide as long, 

 the upper face straight. First costals quadrangular, considerably narrower 

 and shorter than the radials; the second a little longer than the first and 

 pentangular, their sloping upper faces at right angles. Distlchals three in 

 the anterior ray, two only in the antero-lateral ones. In the posterior rays, 

 the divisions next to the anal interradius have two distichals, the others 

 three. All divisions with two distichals are followed by 2 X 2 palmars, those 

 having three directly by free arm plates. Arms sixteen (exceptionally seven- 

 teen, there being sometimes an additional one in the anterior ray) ; simple, 

 slender, pointed at their ends, and incurving ; they are biserial from the 

 second free plate, and provided with slender, long-jointed pinnules. Inter- 

 radial spaces slightly depressed at the arm regions. Regular interbrachials 

 three to four ; the first very large, as wide as high. The anal interradius 

 contains from seven to nine pieces, the anal plate being succeeded by three 

 plates, and these by three and two ; occasionally there is another small plate 

 above, separating the palmars, and a similar plate sometimes occurs at the 

 other sides. Ventral disk subcorneal, and extended into a central anal tube. 

 The plates are but slightly convex and of almost uniform size, except that 

 the posterior oral is twice as large as any of the four others. Column 

 decidedly tapering ; the joints nearest the calyx nearly twice as wide as 

 those two inches farther down, the former with convex edges, the others 

 almost cylindrical, and there are six joints to the last internode that is pre- 

 served in the specimen. 



Horison and Locality. — Keokuk group, near Keokuk, Iowa. 



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



