BATOCRINID. 367 
posterior rays. ‘The arms are simple, 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 around 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. 
Distribution. — Batocrinus ranges from the Kinderhook to the lower part 
of the St. Louis group, and, so far as known, is restricted to America. 
Type of the genus: Batocrinus icosidactylus 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 unfortunately, 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. Satocrinus, as now restricted, differs from Evetmo- 
crinus in having short cylindrical arms in place of paddle-shaped ones, and 
in the greater length of the anal tube. Zutrochocrinus and Dizygocrinus differ 
from both of them in the tendency of the arms to double from the same 
opening. Macrocrinus and Lobocrinus 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 Bafocrinus are sometimes 
slightly flattened towards the tips, but never paddle-shaped like those of 
Eretmocrinus. 
