BATOCRmiDiE. 367 



posterior rays. The arms are simj^le, very short, slightly incurving, and 

 rounded on the back (never spatulate) ; the pinnules stout, deep, closely 

 packed, and flattened at their lateral faces. Interbrachials separated from 

 the interambulacral pieces by the overarching palmars, which form a con- 

 tinuous series aroimd the calyx ; the four regular sides have rarely more 

 than three, of which the first is very large, those of the second row being 

 small, while some species have but one. The anal plate is succeeded by 

 three large pieces, and these variously by one, two, or three interbrachial 

 plates. There are neither interdistichals nor interpalmars. Ventral disk 

 convex ; the plates of nearly uniform size, except the posterior oral, which 

 is larger, more convex, and forms the base of the anal tube on the anterior 

 side. Anal tube central, heavy and long, often reaching twice the length of 

 the arms. Column stout, round ; the axial canal small and pentangular. 



Distrihidion. — Batocrinus ranges from the Kinderhook to the lower part 

 of the St. Louis group, and, so far as known, is restricted to America. 



Tyjie of the genus : Batocrinus icosidactyhis Cass. 



Remarks. — The genus Batocrinus was not accepted by Hall, White, or 

 McChesney, who referred the respective species to Actinocrinus. Meek and 

 Worthen were at first inclined to give it only subgeneric rank, but in 1873 

 recognized it as a full genus, in which they were followed by us in 1881. 

 As the best distinction between Batocrinus and Actinocrinus, Casseday pointed 

 out the closure of the fixed upper brachials over the interbrachial plates, and 

 no doubt this is a most excellent character, and holds good in the typical 

 species of Casseday. But imfortunately, among the species which Meek and 

 Worthen afterwards referred to the genus, there are quite a number in 

 which this rule does not apply, and these species, which have good generic 

 characters of their own, have been eliminated by us, and made the types of 

 independent genera. Batocrinus, as now restricted, differs from Eretmo- 

 crimis in having short cylindrical arms in place of paddle-shaped ones, and 

 in the greater length of the anal tube. Eutrochocrinus and Dizygocrhms differ 

 from both of them in the tendency of the arms to double from the same 

 opening. Macrocrinus and Loiocrinus have the rays lobed and the arms 

 arranged in groups ; in the former the anal tube is large and central, in 

 the latter short and excentric. The arms of Batocrinus are sometimes 

 slightly flattened towards the tips, but never paddle-shaped like those of 

 JEretmocrimis. 



