ACTINOCRINID 2. 593 
PHYSETOCRINUS M. and W. 
1869. Murex and WortHen (Subgenus of Strotocrinus); Proceed. Acad. Nat. Sci. Phila., p.158; also 1873, . 
Geol. Rep. Illinois, Vol. V., p. 349. . 
1881. W. and Sp.; Revision Paleocr., Part II., p. 155 (Proceed. Acad. Nat. Sci. Phila., p. 329). 
1889, S.A. Mittzr; North Amer. Geol. and Paleont., p. 269. 
Arrangement of the plates up to the distichals as in Actinocrinus ; but the — 
anus located within the tegmen, not at the end of a tube. The calyx dis- 
tinctly lobed. The arms arranged in groups, and given off from the two 
main divisions of the rays alternately from opposite sides, But, contrary to 
the case in Actinocrinus, each order of brachials, from the costals up, consists 
of but a single plate, which is axillary, and supports on one side an arm and 
upon the other a brachial of a higher order. Arms biserial. Interbrachials 
numerous, and in contact with the plates of the disk. Ventral disk depressed 
at the summit, plicated around the margin, and generally composed of small, 
irregular pieces. Anus excentric. Column round. 
Mstribution. — Only known from the Burlington group in America, but it 
apparently occurs also in the Mountain limestone of Ireland. 
Type of the genus: Physetocrinus ventricosus. 
Remarks. — Zittel makes Physetocrinus synonymous with Strotocrinus, and 
the latter a subgenus of Actinocrinus. 
Physetocrinus ventricosus (Hatt). 
Plate LXIIM. Fig. 6, and Plate LXIV. Figs. 1, 2, 8, 4, 5,6, 7, and Sa, b. 
1858. Actinocrinus ventricosus — Haun; Geol. Rep. Iowa, Vol. I., Part IL., p. 595, Plate 11, Figs. 6a, 0. 
1873. Physetocrinus ventricosus —Mzunx and WortuEn; Geol. Rep. Illinois, Vol. V., p. 349. 
1881. Physetocrinus ventricosus —W. and Sp.; Revision Paleocr., Part II., p. 157. 
Syn. Actenocrinus subventricosus McCursney; 1860, New Pal. Foss. p. 21 also 1869, Chicago 
Acad. Sci., Vol. I., p. 16, Plate 4, Fig. 6. 
Syn. Physetocrinus subventricosus —MxrnK and Wortuen; Geol. Rep. Illinois, Vol. V., p. 349. 
Syn. Actinocrinus ventricosus var. cancellatus, Haun; 1861, Prelim. Deser. Pal. Foss., p. 3. 
Syn.. Actinocrinus ventricosus, var. internodius Haut; 1861 Bost. Journ. Nat, Hist., p. 278. 
Syn. Actinocrinus ventricosus, var. reticulatus Hat; ibid., p. 279. 
Of more than medium size. Calyx generally as wide as high, somewhat 
higher in young specimens. Dorsal cup basin-shaped ; the sides convex below, 
more rapidly spreading from the top of the distichals; the arm bases pro- 
jecting, deeply grooved between the rays and their main divisions, and 
slightly between the individual arms. Ventral disk hemispherical, varying 
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