a i : / 23 . : ENS ty a : > : 
. L si Met —_ ee Se LL ee ae — ——— 
- = = a 
BATOCRINID#. Dok 
quite uniform; their upper and lower faces striated at the margin, and 
smooth in the middle; axial canal of moderate size. 
Florizon and Locality. —In the Kinderhook group at Le Grand, Marshall 
Co., Iowa, and in both divisions of the Burlington group at Burlington and 
other places. 
Remarks. — There can be no doubt that the specimens of the three beds 
represent one and the same species, although ditfering considerably in size. | 
In the Kinderhook group the specimens are smaller, and only a single dis- , 
tichal takes part in the calyx, while in the Burlington two or three of them | 
are incorporated, and the specimens have proportionally more interbrachial | 
plates. | 
(?) Periechocrinus tenuidiscus (H4tr). 
Plate XLVI. Fig. 4, and Plate LI. Fig. 6. ' 
1861. (°) Actinocrinus tenuidiscus —HatL; Prelim. Descr. New Crin., p. 14. : | | | 
1877. <Actinocrinus tenuidiscus —8. A. MILLER; Catal. Paleeoz. Foss., p. 68. | 
1881. Pertechocrinus tenuidiscus —W.and Sr.; Revision Paleocr., Part IL, p. 133. 
Closely allied to the preceding species, and perhaps a mere variety of the 
same. Dorsal cup more compressed, and distinctly rounded, the arm bases 
less projecting, and the plates ornamented. ‘The plates of the dorsal cup 
covered by broad, ill-defined ridges passing out from near the middle of the 
plates to the margins, where they meet the ridges of adjoining plates. The 
ridges following the brachials more prominent, especially as they approach 
the arm bases. A similar ridge follows the median line of the anal area. 
The surface of the plates is beautifully marked by very fine radiating wrink- | 
les; the plates very thin at their outer margins, and but little thicker in the | 
middle. 
Basals forming a low hexagonal basin, with a slightly projecting rim at 
the bottom; the column facet somewhat concave, occupying one half the 
diameter of the cup. Radials large, nearly as long as wide; the costals con- 
siderably smaller, decreasing in size upwards in the same proportions as the 
radials and first costals. Distichals, so far as observed, two or three in the 
calyx; the two upper ones curved like arm plates. First interbrachial as large 
as the first costals, and as wide as long, those of the second row equal to the 
second costals; the second row has two or three plates, and the succeeding 
ones three or four. Anal interradius very wide; the first anal plate smaller 
than the radials; the three plates overlying it as large as the first inter- 
