SS = Soe Sr eS SS Se Se a SS a 
490 THE CRINOIDEA CAMERATA OF NORTH AMERICA. 
authentic specimens from White’s creek near Nashville, Tenn., Roemer’s 
typical locality, with those from Iowa and Illinois, which Hall described 
and figured as Agaricocrinus tuberosus, shows that the latter are sufficiently 
distinct to be recognized at least as a variety. The two forms resemble each 
other in their general outlines, but the lower face of the calyx in the Iowa 
specimens is considerably more concave; their first interbrachials shorter 
and not visible in a side view, or but very slightly ; the plates of the dorsal 
cup are somewhat more convex, and the anal area is less tumid, and not so 
abruptly protruding as in the typical form of A. americanus. 
Horizon and Locahty. — Keokuk group, Keokuk, Iowa, and at Hamilton, 
Nauvoo, and Niota, Ills. 
Types in the collection of Wachsmuth and Springer. 
Agaricocrinus Wortheni Hatt. 
Plate XX XIX. Fig. 9, and Plate XL. Figs. da, b, ¢, d. 
1858. Hatt; Geol. Rep. Iowa, Vol. I., Part I1., p. 619, Plate 16, Fig. 1. 
1881. W. and Sp.; Revision Paleocr., Part II., p. 113 (Proceed. Acad. Nat. Sci. Phila., p. 287). 
A large species. Calyx depressed pyramidal, pentagonal as seen from 
above or below, the anal side broadly and deeply excavated, and the posterior 
rays distinctly lobed. The plates of the dorsal cup to the middle of the 
second costals placed within a deep concavity, which contains not only the 
basals, radials and first costals, but the whole of the first interbrachials and 
parts of the second. All succeeding: plates of the dorsal cup are stretched 
out almost horizontally, and only the arm facets and the third row of inter- 
brachials are visible in a side view. The plates within the concavity are 
perfectly flat; while all radial plates from the second costals up are more or 
less convex. 
Basals slightly projecting beyond the column. Radials nearly as long as 
wide. The first costals fully as large, or even larger than the radials; hex- 
agonal, their upper angles truncated by the second interbrachials. Second 
costals about twice as large as the first; wider, but not as long. First dis- 
tichals almost as large as the upper costals, their width much greater. The 
second distichals, when represented, are wider than the first, but half their 
length. The posterior rays, which have three or four arms, have but one 
distichal in one or both divisions, which supports on each side a rather large 
palmar, and this, which is formed like an axillary, is followed by the two 
rows of arm plates. Arms twelve to fourteen, long, stout, tapering; com- 
i 
——— 
a 
—a ame Ses eta 
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