48 
SMITHSONIAN INSTITUTION 
Family PLATYCRINIDAE Roemer 
Monocyclic, RR in contact all around. No anal. BB 3, unecjual, forming a 
pentagon. 
This monocyclic family is intermediate between the typical Camerata and the Inadunata. 
As in the latter, the dorsal cup consists chiefly of basal and radial structures, those of inter- 
radial origin being in the later stages largely confined to the tegmen. It had a long geological 
range, from Silurian to Lower Carboniferous, and in the latter its typical forms were fully 
developed, in which the plates above the radials enter but slightly into the cup, and the stem 
becomes remarkably specialized with an elliptical section and transverse ridge. It culminated 
with a great number of characteristic species, in '.vhich the dominant characters may be seen 
and studied to best advantage. 
The Silurian and Devonian stage exhibits some marked variations, but in the main 
embi'aces forms of the simpler and more primitive types, showing the least departure from 
the Camerate plan. While they are for the most part rare, the present collections have yielded 
abundant representatives of two of the subdivisions. In each the material is of exceptional 
importance, because the specimens belonging to some forms occur in such numbers and 
preservation as to afford the means of comparative studies not hitherto possessed on either 
continent, requiring in one case the recognition of a new genus. 
Section i. Subfamily COCCOCRININAE Bather 
Rays with two or more primibrachs. 
The division here first discussed, embracing forms with 2 or more IBr, represents the 
simplest form of the Camerata, the calyx consisting only of 3 BB forming a pentagon, 5 RR, 
2x5 IBr, 5 iBr and 5 orals. The tegmen is almost completely occupied by 5 large triangular 
orals forming a closed pyramid analogous to the larval stage of the crinoids. Anal opening 
is lateral, in the interradio-oral suture, and the arms usually two to the ray. Column round, 
no sign of the elliptic columnals having yet appeared. 
LYONICRINUS new genus 
Plate II 
Pro Coccocrinus bacca Roemer, Sil. Fauna Westl. Tennessee, i860, p. 51. — Cf. Coccocrinus loh. Mtiller, 
in Wirtgen und Zeiler, Verb. Naturh. Verein Rbeinl., 12, 1855, p. 20. — Zittel, Handb. Pal., i, 
1879, P- 347- — Wacbsmutb and Springer, Rev. Pal., pt. 2, 1881, p. 58; pt. 3, 1885, p. 114; N. A. Crin. 
Cam., 1897, p. 738. — Batber, Treatise on Zool, pt. 3, 1900, p. 156. — ^Jaekel, Krinoid. Deutscbl., 1895, 
p. 95 ; Pbylogenie und System, 1918, p. 91. — Zittel-Eastman Textb. Pal., 1913, p. 199. — Bassler, 
Bibliogr. Index, 1915, p. 248. 
Dorsal cup as in the Platycrinidae. Small basal in left posterior position. 
IBr 2. IIBr more than 2. Tegmen composed of 4 large, triangular interambu- 
lacral plates ( ? orals) surrounding a central space, perhaps for posterior oral, 
with open clefts between them for ambulacra ; plus one large posterior plate 
flanked by 2 smaller ones supporting a protuberant anal opening. Arms ten, 
unbranched, uniserial, with quadrangular brachials. 
Genotype. Coccocrinus bacca Roemer. 
Distribution. Silurian ; America. 
This genus is founded upon the species Coccocrinus bacca Roemer, of the Tennessee 
Silurian. Much has been written about the genus Coccocrinus, and it still remains illy under- 
