BATOCRINID^. 419 



brachials, which are covered with small tubercles, for distinct plates. "Whether 

 any multiplication of arms took place in this species is not known. 



Dizygocrinus Whitei W. and Sp. 

 Plate XXXIII. Figs. 10a, b, and Fig. 11. 



ISSl. Biitoerimis Whitei — W. and Sp. ; Eevision Palseocr., Part II., p. 169. 



Sja. Batocrims sjiergenensis S. A. Miller, 1891, Adv. Sheets, 17tli Rep. Geol. Sarv. Indiana, p. 60, 

 Plate 10, Pigs. 5 and 6. 



Calyx small, depressed globose; the dorsal cup equal to, or but little 

 higher than, the ventral disk ; the arm regions slightly projecting. Surface 

 of plates ornamented. The radials and brachials have along their median 

 lines a well defined ridge, and at each side of this ridge, toward the sides of 

 the plates, an angular node, which appears in the specimens as if forming an 

 independent plate. Eidges or rows of small tubercles occur also on the 

 interbrachials, some of them proceeding from the centre of the first plate 

 to the radials, others to the higher interbrachials. 



Basals short, forming a projecting circular rim, with a shallow striated 

 depression for the reception of the column. Eadials twice as wide as long; 

 the sloping upper sides shorter than the corresponding lower ones. Costals 

 considerably shorter and narrower than the radials ; the first quadrangular, 

 the second pentangular. Distichals 2 X 2, of similar form, but smaller than 

 the costals ; in the anterior ray supporting the arms ; in the other rays 

 followed by two rows of palmars. The upper faces of all arm-bearing plates 

 are directed outward, and formed into circular, rather large facets with 

 a notch at the upper end. The surface of these facets is slightly concave, 

 and grooved at the inner margin. Arms eighteen, single, infolding, gradu- 

 ally tapering, and constructed from the second free plate of two series of 

 moderately long pieces. Pinnules very long, composed of joints three times 

 longer than wide. Interbrachials : 1, 2, 1, sometimes with an additional 

 narrow piece between the arms. Anal plate somewhat higher than the 

 radials, and followed variously by 3, 3, and 2 plates or by 3, 2, and 1 ; the 

 latter being generally the case in specimens from the Keokuk group, 

 the former in those from the Warsaw limestone. Plates of the ventral disk 

 of nearly equal size, all covered with a sharp central tubercle. Anal tube 

 long, extended beyond the tips of the arms, constructed of convex plates 

 interspersed with slightly nodose or spinous pieces. Column slender; com- 

 posed of large and smaller joints, the larger ones with convex edges. 



