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BATOCRINID&. 433 
ing a single row of large distichals, and these the free arms, except in the 
posterior rays, in which the plates facing the anal side are axillary, and give 
off two arms, or three to those rays. Arms delicate; composed of two rows 
of rather long joints alternately arranged. Anal plate a little longer than — 
wide, contrary to the radials, which are wider than long; it is followed by 
three and one plate. The other interradii have but one interbrachial, above 
which the distichals meet. Ventral disk highly convex, composed of but 
few large plates, of which the orals occupy almost one half of the whole 
surface. They are surrounded by five large radial plates, between which 
are interposed two or three smaller interambulacral pieces. Anal tube 
nearly central, very thin and short. 
Horizon and Locahty.— Upper Burlington limestone; Burlington, Iowa. 
Type in the Hlinois State collection. 
‘Dizygocrinus andrewsianus (McCuzsyey). 
Plate XXIX. Figs. 2a, b, ¢, d. 
1860. <Actinocrinus andrewsianus — McCursney; New Paleoz. Foss.. p. 27. 
1867. <Actinocrinus andrewsianus —McCuusney; Chicago Acad. Nat. Sci., p. 20, Plate 5, Fig. 5. 
1881. Batocrinus andrewsianus —W. and Sp.; Revision Paleocr., Part II., p. 165 (Proceed. Acad. Nat. 
Sci. Phila., p. 339). 
A small species. Calyx obconical below the arms, the plates smooth and 
almost flat; above the arms conical, and the plates convex, sometimes 
tuberculous. 
Basal cup low saucer-shaped, the sides not projecting ; the column facet 
small, interbasal sutures indistinct. Radials of medium size, wider than long. 
First costals small, quadrangular; the second generally heptangular, a little 
wider than the first, but not quite as long. Distichals two in all the rays; 
but in four of them the upper is axillary, and followed by a row of palmars. 
In the anterior ray, in which there are no palmars, the distichals are some- 
what larger, and the second supports the arms. Arm-bearing plates slightly 
projecting, in contact laterally except at the anal side. Arm openings 
directed outward. Arms long, infolding, rather thin, not touching each 
other laterally ; they are subcylindrical at their bases, somewhat flattened 
and wider at the top. The anal plate, which is as large as the radials and 
of a similar form, is followed by rows of 3, 3, and 2 plates, sometimes 
with an additional piece in the arm regions. The interbrachials of the four 
other sides consist of four plates in three rows. The plates of the ventral 
disk are moderately large and of nearly the same size; the anal tube is sub- 
central, rather thin and short, not extending beyond the tips of the arms. 
55 
