12 
SMITHSONIAN INSTITUTION 
Order CAMERATA Wachsmuth and Springer 
Crinoidea in which the lower brachials take part in the dorsal cup. All plates of 
CALYX UNITED BY CLOSE SUTURE AND IMMOVABLE. MoUTH AND FOOD-GROOVES COMPLETELY 
COVERED, THE COVERING PIECES OF THE LATTER FREQUENTLY INCORPORATED IN THE TEG- 
MEN. Anal opening excentric of subcentral, frequently at the end of a tube. 
Arms uniserial or biserial, and pinnulate. 
The crinoids of this order constitute more than half of those herein treated, embracing 
31 genera of which 7 are new, and 43 new species out of a total of 103. Important new light 
is shed upon some forms heretofore not well understood such as Gazacrinus, Lampterocrinus 
and Lyonicrinus. The most prolific of the genera is Marsipocrmns, hitherto accounted rare, 
which now appears from the Tennessee area to the number of 10 species, some of them in a 
preservation and with a wealth of individuals before unknown. 
Family DIMEROCRINIDAE Bather 
This family, embracing substantially all dicyclic Camerata with truncate 
post. B in which the RR are in contact except at the anal side, while it has an 
extreme range from Ordovician to Devonian, is essentially a Silurian form, of 
which we have four well marked genera in the present collection. 
DIMEROCRINUS Phillips 
Plate I 
Dimerocrinitcs Phillips in Murchison’s Sil. Syst., 1839, p. 674. 
Dimerocrinus D’Orbigny, Prodr. Pah, i, 1850, p. 46. — Wachsmuth and Springer, Rev. Pah, 2, 1881, pp. 184, 
197. — Bather, Treatise on Zooh (Lankester), 3, 1900, p. 198. — Zittel-Eastman, Textb. Pah, 2d Ed., 
1913, p. 187. — Jaekel, Phylogenie und System, 1918, p. 41. — Bassler, Bibliogr. Index, Bull. 92, U. S. 
Nat. Mus., 1915, p. 438. 
Thysanocrinus Hall, Pah New York, 2, 1852, pp. 188, 355. — Wachsmuth and Springer, N. A. Crin. Cam., 
1897, p. 190. 
Glyptaster Hall, Pah New York, 2. 1852, p. 187; 28th Rep. New York St. Mus., 1879, p. 131. — Wachsmuth 
and Springer, Rev. Pah, 2, 1881, p. 193. 
Eucrinus Angelin, in part. Icon. Crin. Suecc., 1878, p. 198. 
Calyx rather elongate; IBB 5 ; post. B truncate; first anal plate in line with 
RR, followed by 3 in second range; iBr in several ranges; anus without a tube; 
arms biserial, simple, 2 or 4 to the ray, directed upwards ; column round. 
Genotype. Dimerocrinus decadactylns Phillips. 
Distribution. Silurian ; England, Gotland, America. 
This genus is well represented in the English Silurian under Phillips’ type from Dudley, 
in Gotland by several species under the name Eucrinus, and in America by a series of species 
under Thysanocrinus and Glyptaster, to which must now be added important new forms from 
the Tennessee collections. In the monograph of Crinoidea Camerata of 1897 priority was 
given to the name Thysanocrinus, a course which has since been modified in favor of the per- 
fectly recognizable type described by Phillips. 
