BATOCRINID &. 49] 
posed of two series of ninety or more joints to each series. Interbrachials: 
1, 2, 3; the first very short and small for the genus, not rising to the full 
height of the first costals; the two of the second row twice as long as the 
first and very narrow; the plates of the third range quite variable in form 
and size, and partly interambulacral. First anal plate larger than the radials, 
and longer than wide; deeply truncated at the upper angles for the support 
of two large, elongate interbrachials, which enclose a narrow second anal. 
There are four to five plates in the next range, which are followed by nume- 
rous small, irregular pieces, forming a flattened area containing the anus, 
which is directed obliquely upwards; the plates of this area grow smaller as 
they approach the anus, which is located midway between the posterior oral 
and arm regions, and opens out laterally. Ventral disk depressed conical ; 
the orals and radial dome plates large and covered with heavy rounded 
nodes, which extend over the whole surface of the plates; the intervening 
pieces are comparatively small and but slightly convex. Posterior oral 
extremely large, and separated by small perisomic plates from the other 
four, and similar plates are interposed between the latter, so each oral is 
isolated. There is one large radial dome plate over each anterior ray, and 
two over each posterior one, the second plate being placed above the division 
with two arms. The interambulacral plates are quite numerous, and cover 
over the origin of the ambulacra. 
Horizon and Locality.— Upper part of the Keokuk group; Keokuk, 
Iowa, and Hamilton, Ills. 
Type in the (Worthen) Illinois State collection, Springfield. 
Ltemarks. — This species is readily distinguished from A. americanus by 
its larger size, the hexangular form of the first costals, the different arrange- 
ment of the interbrachial pieces, the isolated condition of the orals, and the 
flatness of the anal area. 
Agaricocrinus excavatus Hatt. 
Plate XX XIX. Figs. 3, 4, 8. 
1861. Agaricocrinus excavatus —Hau; Prelim. Deser. New Spec. Crin., p. 3. 
1861. Agaricocrinus (Amphoracrinus) excavatus — Hat; Bost. Journ. Nat. Hist. Vol. VIL., p. 282. 
1877. Amphoracrinus excavatus-—S. A, Mittur; Catal. Amer. Paleoz. Foss., p. 70. 
1893. Agaricocrinus excavatus — WHITFIELD; Mem. Amer. Mus. Nat. Hist., 1898, Vol. L, p. 26, Plate 2, 
Figs. 14, 16. 
Smaller than the two preceding species. Calyx pyramidal, a little wider 
than high; the radial portions projecting outward and downward so as to 
