BATOCRINID &. A89 
narrow and very long, curving abruptly from the basal concavity to the 
upper edge of the dorsal cup, then tapering and rising somewhat beyond 
the second interbrachials which lie at both sides of it; the latter forming 
extremely narrow strips, which rest against the curved up lateral faces of the 
second distichals. Ventral disk subpyramidal, the interradial spaces slightly 
depressed; plates highly convex, except the interambulacral pieces, which are 
almost flat and considerably smaller. Surface of the plates finely granulose. 
The posterior oral, which is as large as any two of the others, and slightly - 
excentric in position, is surrounded by eight plates: viz., the four smaller 
orals, two large anal pieces, and two radial dome plates of almost the 
same size as the orals. Near the periphery there is over each ray another 
large radial plate, and over the posterior ray toward the anal side a second 
smaller one, which is wanting in the rays with two arms. The interam- 
bulacrals consist of five to six pieces, and two, other plates overlie the 
ambulacra. Column comparatively narrow; the nodal joints slightly wider, 
with convex outer faces. 
Horizon and Locality. — Keokuk group; White’s creek, near Nashville, 
Tenn., and Pilot Knob, near Louisville, Ky. , 
Tye in the Mineralogical Museum at Breslau. 
Remarks. — This species is remarkable for the extreme length of its first 
interbrachial pieces, rising as they do to the top of the dorsal cup, and the 
great tumidity of the anal area, which, together with the form of the calyx, 
distinguishes it readily from the other species. 
In 1878* we placed Agaricocrinus bullatus Hall, A. excavatus Hall, and 
A. nodosus Meek and Worthen as synonyms under this species. Since then 
we obtained a large number of additional specimens, especially from the 
typical locality, which show that these forms can be specifically separated. 
Agaricocrinus Americanus, var. tuberosus (Hatr) W. and Sp. 
Plate XL. Fig. 6, and Plate XLII. Fig. 4. 
1850. Troost; List of Crin. Tenn. (Proceed. Am. Ass. Adv. Sci. Cambr. Meet., p. 60). 
1850. Hat; Geol. Rep. Iowa, Vol. I., Part IL, p. 617, Plate 16, Figs. 2a, 0, c. 
The specimens for which we propose this variety have been generally 
‘regarded as synonymous with A. americanus. A comparison, however, of 
* Proceed. Acad. Nat. Sci. Phila., p. 240. 
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