BATOCRmiD^. 371 



Batocrinus aectualis (Hall). 

 Plate XXVIII. Figs. 5, 6. 



1858. Jctlnocrinus irqiitiUs — Hall; Geol. Rep. Iowa, Vol. I., Part II., p. 592, Plate 11, Pigs, ia, b. 

 1873. JSatocrinus tsqiialis — M. and W. ; Geol. Rep. Illinois, Vol. V., p. 367. 

 1881. Batocrinus tequalis — W. and Sp. ; Revisiou Palteocr., Pait II,, p. 165. 



Syn. Aciinocrinus doris — Hall, 1861 ; Descr. New Spec. Crin., p. 15. 



Syn. Batocrinus doris — M. and W. ; Geol. Rep. Illiuois, Vol. V., p. 367. 



Closely allied to the preceding species, but differing in the greater 

 number of arms. Calyx biturbinate, truncate at the bottom ; the dorsal 

 cup a little higher than the ventral disk ; the sides abruptly spreading to 

 the arm bases, which are directed horizontally ; the plates smooth, highly 

 convex. 



Base short, excavated for the reception of the column, the interbasal 

 sutures deepty grooved, giving to the lower end a trilobate outline. Eadials 

 smaller than the basals, from once and a half to twice as wide as long. First 

 costals less convex than the surrounding plates, quadrangular, variable in 

 size, sometimes but half the width of the radials and very short. Second 

 costals wider and longer than the first. Distichals 2X2; supporting in 

 four of the rays two rows of three plates, and these four arms to the rays. 

 In the two posterior rays, which have from six to seven arms, both outer 

 distichals of the rays support an axillary palmar, which is followed by 2 X 2 

 post-palmars ; while the two inner distichals support but 2 palmars. When 

 there are seven arms, one of the post-pahnars is also axillary and gives off 

 two arms instead of one. Arms short, cylindrical, biserial from their bases ; 

 the plates short. Pinnules long. Kegular interbrachials two or three, the 

 first very large. The anal area consists of five plates ; the anal plate, which 

 is larger than the radials, is succeeded by three plates in the second row, and 

 a small piece above. At all sides the interbrachial plates are separated from 

 the dome plates by the palmars, and post-palmars respectively, which form 

 together with adjoining distichals and costals around the plates of the anal 

 area a well defined semicircle. Ventral disk conical, gradually passing into 

 the anal tube ; the plates strong and convex. The orals and ambiilacral 

 plates are much larger than the intervening ones, which latter are com- 

 paratively small and numerous at the posterior side. Anal tube central, 

 its plates slightly tumid. Column similar to that of the preceding species. 



Horizon and Locality. — Lower Burlington limestone ; Burlington, Iowa, 

 and Southern Mi.ssouri. 



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



