CYATHOCRINIDAE 
I3I 
Family CYATHOCRINIDAE Roemer 
Dicyclic; IBB usually 5. Radial facets usually semicircular, less than 
width of radial ; union with brachials by incomplete articulation, without trans- 
verse ridge. Arms uniserial, non-pinnulate, mostly dichotomous. Tegmen com- 
posed of rather large orals, rigid ambulacrals, which often encroach upon and 
obscure the other plates. 
Thalamocrinus Miller and Gurley 
Plate 26 
Miller and Gurley, Bull. 7, Illinois St. Mus., 1895, p. 82. — Bather, Treatise on Zool., 3, 1900, p. 204. 
Dicyclic. IBB 5, large, about one third the height of cup ; BB still larger, 
nearly half the height of cup; RR much shorter, not over one sixth the height 
of cup; radial facets curved, shallow, narrower than RR, directed upward. 
RA small, rhombic, abutting on x, supported by post, and r. post. BB. Anal x 
small, in line with RR. Arms slender, with elongate brachials, uniserial, num- 
ber unknown. 
Genotype. Thalamocrinus ovatus Miller and Gurley. 
Distribution. Silurian to Devonian ; America. 
This genus falls under the Carabocrininae subdivision of the Cyathocrinidae, with RA 
similar to that of Palaeocrinus. It is rather near to Homocrinus, as interpreted by Bather in 
connection with his Gotland species, Grin. Goth, p. loi, pi. 4, figs. 143-147, but has narrower 
facets and more simple arms. Miller and Gurley mention the “ radials or third series of 
plates ” as six, thus including what we know as the anal x. They missed the important ele- 
ment, the radianal, both in their descriptions and figures ; but it appears plainly in all four of 
the species, including some of the specimens examined by the authors from the collection of 
Mrs. Milligan. It is a rare form, and most of the principal specimens are figured here. 
Thalamocrinus ovatus Miller and Gurley 
Plate 26, figs. 2-g 
Miller and Gurley, Bull 7, Illinois St. Mus., 1895, p. 82, pi. 5, figs. 29-31. — Miller, N. A. Geol. Pal., 2d App., 
1897, p. 754> fig. 1402. 
Characterized by its elongate ovoid form, which is well maintained among 
several specimens, the great height of BB, and constriction at the distal mar- 
gin, whereby the space is reduced to very narrow facets for slender arms. In 
the only specimen with any part of the arms preserved they are shattered so that 
little can be seen except the displaced brachials, which are long, narrow and 
rounded; it is evident that the arms were long and slender, probably simple or 
only branching once. 
Horizon and locality. Beech River formation, Niagaran ; Decatur County, Tennessee. 
